Camera and distance measuring method thereof

ABSTRACT

The present invention provides a camera where a focusing position of a taking lens is adjusted as a first focus adjustment by a CPU, and as a second focus adjustment lower in accuracy but higher at a speed than the first focus adjustment. An object image is picked up through the taking lens by an imager, and an output signal of the imager is converted into image data. A compressibility of the image data obtained at the imager is set by an image processing section, and the image data is compressed in accordance with the set compressibility. Then, in accordance with the compressibility set by the image processing section, the CPU decides which of the first focus adjustment and the second focus adjustment is used to execute a final focus adjustment operation of the taking lens.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Applications No. 2002-247359, filed Aug. 27,2002; No. 2002-314449, filed Oct. 29, 2002; No. 2002-324016, filed Nov.7, 2002; and No. 2002-325266, filed Nov. 8, 2002, the entire contents ofall of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a focusing technology of an electroniccamera, and more particularly to a camera which can change acompressibility when an electronic image is stored, and switch afocusing method.

2. Description of the Related Art

Additionally, the present invention relates to an improvement of aso-called autofocus technology of a digital camera which electronicallyrecords an object image obtained through a taking lens by an imager.

In focusing of the electronic camera, a system called a climbing typeimager AF (autofocus) which uses a photographing imager but no specialsensors is often used.

In the imager AF, however, it is necessary to monitor a change made incontrast of the object on the imager in accordance with a focusingposition of the taking lens, and a time lag during releasing oftenbecomes a problem.

Thus, different focusing systems are disposed to correct the problem.For example, see Jpn. Pat, Appln. KOKAI Publication Nos. 2001-141985,2001-249267, 2001-255456 etc.

On the other hand, various improvements have been made regarding imagecompression. The applicant of the present invention has filed Patent No.3115912 etc. This regards a technology of changing a compressibilityduring image recording by using information obtained when the imager AFis operated. Similar technologies are disclosed in Jpn. Pat. Appln.KOKAI Publication No. 2000-201287 etc.

An advantage of the imager AF is that even if there is an error in astop position of the taking lens, a focusing position including theerror is controlled, and thus feedback control which cancels the errorcan be carried out even in the case of lens position characteristicsdifferent from design due to a temperature, humidity or posturedifference etc.

However, since it takes time until focusing as described above, in thecameras described in Jpn. Pat. Appln. KOKAI Publication Nos. 2001-141985and 2001-249267, in a situation of a large focal depth, the previouslens position error is ignored, and focus control (LD) is carried outonly based on a result of an external light AF.

In the distance measurement apparatus described in Jpn. Pat. Appln.KOKAI Publication No. 2001-255456, two systems are switched depending ona mode.

However, there may be a scene to be focused more accurately even if afocal depth is large, and a scent to be photographed by eliminating arelease time lag even if a focal depth is small. Thus, setting by a modeis burdensome. Therefore, if priority can be switched between focusingand a time lag depending on a scene, it is possible to provide a cameramore satisfactory to a user.

BRIEF SUMMARY OF THE INVENTION

Accordingly, a first object of the present invention is to provide acamera which optimally combines an AF system with a compression systemin accordance with photographer's intension to enable high-speedphotographing, and which can effectively use a capacity of a recordingmedium.

A second object of the present invention is to provide an autofocuscamera which has, e.g., a multipoint distance measuring function,determines an intended photographing type (i.e., whether priority is onfocusing or a time lag) of a photographer depending on a photographicscene, and can set distance measuring and a shutter speed suited to thescene, for example without any release time lags or losses of a photoopportunity.

A third object of the present invention is to provide a camera whichcarries out accurate photographic scene detection, can photograph thescene by selecting a focusing system optimal to the scene, and has nounsatisfactory time lags or focusing accuracy, a distance measuringapparatus, a camera distance measuring method, and a distance measuringmethod.

A fourth object of the present invention is to provide an easy-to-usecamera which employs a focusing method optimal to a scene, and providesfocusing accuracy and a time lag satisfactory to a photographer even ina scene where focusing accuracy is important, or a scene where a highspeed is necessary, and a distance measuring method.

A first feature of the present invention is directed to a cameracomprising:

-   -   a taking lens;    -   a first focus adjustment section which adjusts a focusing        position of the taking lens;    -   a second focus adjustment section which has accuracy lower than        that of the first focus adjustment section but which adjusts the        focusing position of the taking lens at a high speed;    -   an imaging section which includes an imager to image an object        image through the taking lens, and converts an output signal of        the imager into image data;    -   a compressibility setting section which sets a compressibility        of the image data obtained in the imaging section;    -   a compression section which compresses the image data in        accordance with the compressibility set in the compressibility        setting section; and    -   a deciding section which decides one of the first focus        adjustment section and the second focus adjustment section which        is employed to carry out a final focus adjustment operation of        the taking lens in accordance with the compressibility set in        the compressibility setting section (corresponding to claim 1).

A second feature of the present invention is directed to a cameracomprising:

-   -   a taking lens;    -   an imaging section which includes an imager to image an object        image through the taking lens, and converts an output signal of        the imager into image data;    -   a first focus adjustment section which adjusts a focusing        position of the taking lens by detecting a contrast change of        the image data outputted from the imaging section during        movement of the taking lens;    -   a second focus adjustment section which includes a section to        output a signal dependent on a distance of an object, and        adjusts the focusing position of the taking lens in accordance        with an output result of the section;    -   an image processing section which carries out predetermined        processing for the image data outputted from the imaging        section; and    -   a control section which causes one of the first focus adjustment        section and the second focus adjustment section to execute a        final focus adjustment operation for the taking lens in        accordance with a processing content of the image processing        section (corresponding to claim 5).

A third feature of the present invention is directed to a cameracomprising:

-   -   a taking lens;    -   an imaging section which includes an imager to image an object        image through the taking lens, and converts an output signal of        the imager into image data;    -   a compressibility setting section which sets a compressibility        of the image data obtained in the imaging section;    -   a compression section which compresses the image data in        accordance with the compressibility set in the compressibility        setting section;    -   a first focus adjustment section which adjusts a focusing        position of the taking lens by detecting a contrast change of        the image data outputted from the imaging section during        movement of the taking lens;    -   a second focus adjustment section which includes a section to        output a signal dependent on a distance of an object, and        adjusts the focusing position of the taking lens in accordance        with an output result of the section; and    -   a control section which operates the second focus adjustment        section alone when the compressibility set in the        compressibility setting section is a first compressibility, and        which operates the first focus adjustment section after the        second focus adjustment section when the compressibility is a        second compressibility lower than the first compressibility        (corresponding to claim 9).

A fourth feature of the present invention is directed to a cameracomprising:

-   -   a taking lens;    -   an imager which images an object image through the taking lens;    -   an image processing circuit which generates digital image data        from an output of the imager, and includes a compression circuit        to compress the image data at a compressibility selected from a        plurality of compressibilities;    -   a focus adjustment mechanism which adjusts a focusing position        of the taking lens;    -   a distance measuring circuit which detects a distance of an        object or a focus deviation amount of the taking lens; and    -   a CPU which receives the output of the imager and an output of        the distance measuring circuit, controls the focus adjustment        mechanism based on the received outputs, and decides a control        form of the focus adjustment mechanism in accordance with the        compressibility selected by the compression circuit        (corresponding to claim 10).

A fifth feature of the present invention is directed to a cameracomprising:

-   -   a contrast detection section which detects contrast of an object        image signal obtained through a taking lens;    -   a multipoint distance measuring section which can range a        plurality of points in a photographic screen through a pair of        optical systems different from the taking lens;    -   a first focus adjustment section which focuses the taking lens        in accordance with a detection result of the contrast detection        section;    -   a second focus adjustment section which focuses the taking lens        based on a distance measuring result of the multipoint distance        measuring section;    -   a position determination section which determines a position of        a main object in the photographing screen from the distance        measuring result of the plurality of points; and    -   a selection section which operates the first focus adjustment        section when the position determination section determines that        the main object is positioned on a center, and which operates        the second focus adjustment section when the main object is        determined to be positioned on a periphery in the photographing        screen (corresponding to claim 13).

A sixth feature of the present invention is directed to a cameracomprising:

-   -   a first autofocus section which focuses a taking lens based on        contrast of an object image signal obtained through the taking        lens;    -   a second autofocus section which can range a plurality of points        in a photographic screen through a pair of optical systems        different from the taking lens, and focuses the taking lens        based on a distance measuring result thereof; and    -   a selection section which preferentially operates the second        autofocus section when it is determined from the distance        measuring result of the plurality of points that a main object        is positioned on a periphery in the photographing screen        (corresponding to claim 14).

A seventh feature of the present invention is directed to a cameracomprising:

-   -   a multipoint distance measuring section which ranges a plurality        of points in a photographic screen by using an optical system        other than a taking lens to obtain a distance to a main object        and a position in the photographing screen;    -   a contrast detection section which obtains an object image        through a predetermined taking lens, and detects contrast        information of the object image; and    -   a control section which focuses the taking lens based on the        contrast information detected by the contrast detection section        when the multipoint distance measuring section determines that        the main object is positioned on a center of the photographic        screen (corresponding to claim 15).

An eighth feature of the present invention is directed to a cameracomprising:

-   -   a determination section which determines a position of a main        object in a photographic screen;    -   a contrast detection section which obtains an object image        through a predetermined taking lens, and detects contrast        information of the object image; and    -   a control section which focuses the taking lens based on the        contrast information detected by the contrast detection section        when the determination section determines that the main object        is positioned on a center of the photographic screen        (corresponding to claim 16).

A ninth feature of the present invention is directed to a camera whichhas a zoom lens in a taking lens, comprising:

-   -   a multipoint distance measuring section which ranges a plurality        of points in a photographic screen by using an optical system        different from the taking lens;    -   a contrast focusing section which decides a focusing position        based on contrast of a photographing target obtained through the        taking lens;    -   a zoom position detection section which detects a zoom position        of the taking lens; and    -   a deciding section which decides whether or not to actuate the        contrast focusing section in accordance with the zoom position        and a result of the multipoint distance measuring (corresponding        to claim 17).

A tenth feature of the present invention is directed to a cameracomprising:

-   -   a first switch turned ON before photographing, and a second        switch turned ON by an operation of a photographing timing;    -   a distance measuring section which measures a distance of an        object by an optical system different from a taking lens by a        timing of the first switch; and    -   a control section which controls a focusing device based on        contrast of an image signal obtained through the taking lens        when a timing of operating the first switch and a timing of        operating the second switch are different from each other by        predetermined time or more, and focuses the taking lens based on        an output of the distance measuring section when the timing of        operating the first switch and the timing of operating the        second switch are less than the predetermined time        (corresponding to claim 19).

An eleventh feature of the present invention is directed to a camerawhich has a focus lock button to execute focus lock control beforephotographing, comprising:

-   -   a control section which carries out no focusing based on        contrast of an image signal obtained through a predetermined        taking lens when the focus lock button is operated, and    -   carries out focusing based on an output result of distance        measuring by an optical system different from the taking lens        (corresponding to claim 20).

A twelfth feature of the present invention is directed to a cameracomprising:

-   -   a taking lens;    -   an imager which images an object image through the taking lens;    -   an image processing circuit which generates digital image data        from an output of the imager;    -   a focus adjustment mechanism which adjusts a focusing position        of the taking lens;    -   a distance measuring optical system;    -   a distance measuring circuit which detects a distance of an        object for a plurality of points in a photographing screen        through the distance measuring optical system; and    -   a CPU which receives outputs of at least the image processing        circuit and the distance measuring circuit, determines a        position of a main object from a plurality of distance measuring        results outputted from the distance measuring circuit, and        decides a control method of the focus adjustment mechanism in        accordance with a result of the determination (corresponding to        claim 21).

A thirteenth feature of the present invention is directed to a cameracomprising:

-   -   a first autofocus section which focuses a taking lens based on        contrast of an object image signal obtained through the taking        lens;    -   a second autofocus section which focuses the taking lens in        accordance with an output of a distance measuring device having        a distance measuring optical system different from the taking        lens;    -   a blurring detection section which detects blurring of the        camera; and    -   a selection section which selects one of the first autofocus        section and the second autofocus section based on an output of        the blurring detection section (corresponding to claim 24).

A fourteenth feature of the present invention is directed to a cameracomprising:

-   -   a distance measuring section which executes distance measuring        by obtaining an image signal in a photographic screen through an        optical system other than a taking lens, and obtains a main        object distance and the image signal; and    -   a control section which determines a blurring state based on a        time change of the image signal obtained by the distance        measuring section, carries out focus control of the taking lens        in accordance with a result of the distance measuring when the        blurring state is determined, and in accordance with contrast of        the object image obtained by the taking lens when no blurring        state is determined (corresponding to claim 25).

A fifteenth feature of the present invention is directed to a distancemeasuring device comprising:

-   -   a distance measuring section which obtains an image signal in a        photographic screen through an optical system other than a        taking lens to carry out distance measuring before        photographing, and obtains a main object distance and the image        signal;    -   a determination section which determines a blurring state; and    -   a switching section which switches between execution of distance        measuring by the distance measuring section based on the        blurring state determined by the determination section and        execution of distance measuring based on contract of the object        image obtained by the taking lens (corresponding to claim 26).

A sixteenth feature of the present invention is directed to a camerawhich has a zoom lens in a taking lens, comprising:

-   -   a distance measuring section which obtains an object image        signal by an optical system different from the taking lens, and        measures a distance of an object;    -   a contrast focusing section which decides a focusing position        based on a contrast change obtained by an imaging section        through the taking lens during very small driving of the taking        lens;    -   a zoom position detection section which detects a zoom position        of the taking lens; and    -   a deciding section which decides whether or not to continue the        contrast focusing control in accordance with the zoom position        and the image signal by the distance measuring section        (corresponding to claim 30).

A seventeenth feature of the present invention is directed to a distancemeasuring method of a camera, comprising:

-   -   a first step of focusing a taking lens by a first autofocus        system based on contact of an object image signal obtained        through the taking lens;    -   a second step of focusing the taking lens by a second autofocus        system in accordance with a distance measuring result of a        distance measuring device which has a pair of optical systems        different from the taking lens;    -   a third step of detecting a change in the image signal used to        enable distance measuring in a photographic screen of the        distance measuring device during control of the first autofocus        system; and    -   a fourth step of selecting focusing by the second autofocus        system when the change of the image signal is detected        (corresponding to claim 32).

An eighteenth feature of the present invention is directed to a distancemeasuring method of a camera, comprising:

-   -   a first step of executing first autofocusing to focus a taking        lens based on contact of an object image signal obtained through        the taking lens;    -   a second step of executing second autofocusing to focus the        taking lens in accordance with a distance measuring result of a        distance measuring device which has a pair of optical systems        different from the taking lens and can execute distance        measuring in a photographic screen by using the image signal;        and    -   a third step of selecting execution or nonexecution of distance        measuring by the second autofocus system based on a time change        in an output of the first autofocusing (corresponding to claim        33).

A nineteenth feature of the present invention is directed to a distancemeasuring method of a camera, comprising:

-   -   a first step of obtaining an image signal in a photographic        screen by using an optical system other than a taking lens to        carry out distance measuring before photographing, and obtaining        a main object distance and the image signal;    -   a second step of determining a blurring state based on a time        change in the image signal obtained by the distance measuring;        and    -   a third step of focusing the taking lens in accordance with a        result of the distance measuring when a blurring state is        determined by the determination step, and in accordance with        contrast of the object image obtained by the taking lens when no        blurring state is determined (corresponding to claim 34).

A twentieth feature of the present invention is directed to a distancemeasuring method comprising:

-   -   a first step of obtaining an image signal in a photographic        screen by using an optical system other than a taking lens to        carry out distance measuring before photographing, and obtaining        a main object distance and the image signal;    -   a second step of determining a blurring state; and    -   a third step of switching between execution of distance        measuring based on the blurring state determined by the second        step and execution of distance measuring based on contrast of        the object image obtained by the taking lens (corresponding to        claim 35).

A twenty-first feature of the present invention is directed to a cameracomprising:

-   -   a taking lens;    -   an imager which images an object image through the taking lens;    -   an image processing circuit which generates digital image data        from an output of the imager;    -   a focus adjustment mechanism which adjusts a focusing position        of the taking lens;    -   a distance measuring optical system different from the taking        lens;    -   a distance measuring circuit which detects a distance of an        object through the distance measuring optical system, and        includes a distance measuring sensor to detect a partial object        image in a photographic screen; and    -   a CPU which controls the focus adjustment mechanism based on an        output of the imager, determines a blurring state from an output        signal of the distance measuring sensor, and cancels a focus        adjustment operation based on the output of the imager when the        amount of blurring is large (corresponding to claim 36).

A twenty-second feature of the present invention is directed to a cameracomprising:

-   -   a taking lens;    -   an imager which images an object image through the taking lens;    -   an image processing circuit which generates digital image data        from an output of the imager;    -   a focus adjustment mechanism which adjusts a focusing position        of the taking lens;    -   a distance measuring optical system different from the taking        lens;    -   a distance measuring circuit which detects a distance of an        object through the distance measuring optical system, and        includes a distance measuring sensor to detect a partial object        image in a photographic screen; and    -   a CPU which controls the focus adjustment mechanism to control a        focus of the taking lens, determines presence of blurring based        on an output signal of the distance measuring sensor, executes        focus control of the taking lens based on the output of the        imager when no blurring is present, and based on an output of        the distance measuring circuit when blurring is present        (corresponding to claim 38).

A twenty-third feature of the present invention is directed to a cameracomprising:

-   -   a first autofocus system which focuses a taking lens based on        contrast of an object image signal obtained through the taking        lens; and    -   a second autofocus section which focuses the taking lens in        accordance with a distance measuring result of a distance        measuring device having a pair of optical systems different from        the taking lens;    -   wherein the distance measuring device can range a plurality of        points in a photographic screen, and comprises a selection        section which preferentially carries out focusing by the second        autofocus system when a main object and other objects are        determined to be in a predetermined distance range based on a        distance measuring result of the plurality of points        (corresponding to claim 39).

A twenty-fourth feature of the present invention is directed to a cameracomprising:

-   -   a first autofocus system which focuses a taking lens based on        contrast of an object image signal obtained through the taking        lens;    -   a second autofocus section which focuses the taking lens in        accordance with a distance measuring result of a distance        measuring device having a pair of optical systems different from        the taking lens;    -   wherein the distance measuring section can range a plurality of        points in a photographic screen, and comprises a switching        section to carry out distance measuring by switching between the        first autofocus system and the second autofocus system        (corresponding to claim 40).

A twenty-fifth feature of the present invention is directed to a cameracomprising:

-   -   a multipoint distance measuring section which ranges a plurality        of points by using an optical system other than a taking lens to        obtain a main object distance and a position in a screen before        photographing; and    -   a control section which carries out focus control of the taking        lens in accordance with a result of the distance measuring when        the multipoint distance measuring section determines that the        main object is present at a distance not different from those of        other objects, and in accordance with contrast of the object        image obtained by the taking lens when the main object is        determined to be present at a distance far from the other        objects (corresponding to claim 41).

A twenty-sixth feature of the present invention is directed to a camerawhich has a zoom lens in a taking lens, comprising:

-   -   a multipoint distance measuring section which measures distances        of a plurality of points in a screen by an optical system        different from the taking lens;    -   a contrast focusing section which decides a focusing position        based on contrast of an imaging section-obtained through the        taking lens;    -   a zoom position detection section which detects a zoom position        of the taking lens; and    -   a deciding section which decides whether or not to actuate the        contrast focusing control in accordance with the zoom position        and a relation between a main object and a background based on a        result of the multipoint distance measuring section        (corresponding to claim 42).

A twenty-seventh feature of the present invention is directed to acamera comprising:

-   -   a first autofocus system which focuses a taking lens based on        contrast of an object image signal obtained through the taking        lens, and    -   a second autofocus section which focuses the taking lens in        accordance with a distance measuring result of a distance        measuring device having a pair of optical systems different from        the taking lens,    -   wherein the distance measuring device can range a plurality of        points in accordance with image signals of the plurality of        points in a photographic screen, and    -   comprises a differentiation section to obtain differentiation        data of the image signals, and    -   a selection section which preferentially carries out focusing by        the second autofocus system when the differentiation information        is higher than a predetermined level (corresponding to claim        44).

A twenty-eighth feature of the present invention is directed to a cameracomprising:

-   -   a first autofocus system which focuses a taking lens based on        contrast of an object image signal obtained through the taking        lens,    -   a second autofocus section which focuses the taking lens in        accordance with a distance measuring result of a distance        measuring device having a pair of optical systems different from        the taking lens,    -   wherein the distance measuring section can range a plurality of        points in accordance with image signals of the plurality of        points in a photographic screen, and    -   comprises a determination section to detect contrast information        in the photographic screen, and to determine a size of the        contrast, and    -   a switching section to switch between the first autofocus system        and the second autofocus system based on a result of the        determination section (corresponding to claim 45).

A twenty-ninth feature of the present invention is directed to adistance measuring method of a camera which has a zoom lens in a takinglens, comprising:

-   -   a first step of executing multipoint distance measuring to        measure distances of a plurality of points in a screen by an        optical system different from the taking lens;    -   a second step of deciding a focusing position based on contrast        of a photographed image obtained through the taking lens;    -   a third step of detecting a zoom position of the taking lens;        and    -   a fourth step of deciding whether or not to actuate contrast        focusing to decide the focusing position based on the zoom        position and a relation between distances of a main object and a        background in accordance with a result of the multipoint        distance measuring (corresponding to claim 48).

A thirty feature of the present invention is directed to a distancemeasuring method of a camera, comprising:

-   -   a step of focusing a taking lens by a first autofocus system        based on contact of an object image signal obtained through the        taking lens;    -   a step of focusing the taking lens by a second autofocus system        in accordance with a distance measuring result of a distance        measuring device which has a pair of optical systems different        from the taking lens, and which can range a plurality of points        in accordance with image signals of the plurality of points in a        photographic screen;    -   a step of obtaining differentiation information of the image        signals; and    -   a step of making selection to preferentially execute focusing by        the third autofocus system when the differentiation information        is higher than a predetermined level (corresponding to claim        50).

A thirty-first feature of the present invention is directed to adistance measuring method of a camera, comprising:

-   -   a step of focusing a taking lens by a first autofocus system        based on contrast of an object image signal obtained through the        taking lens;    -   a step of focusing the taking lens by a second autofocus system        in accordance with a distance measuring result of a distance        measuring device which has a pair of optical systems different        from the taking lens, and which can range a plurality of points        in accordance with image signals of the plurality of points in a        photographic screen;    -   a step of detecting contrast information in the photographic        screen, and determining a size of the contrast; and    -   a step of switching between the first autofocus system and the        second autofocus system based on a result of the determination        (corresponding to claim 51).

A thirty-second feature of the present invention is directed to a cameracomprising:

-   -   a taking lens;    -   an imager which images an object image through the taking lens;    -   an image processing circuit which generates digital image data        from an output of the imager;    -   a focus adjustment mechanism which adjusts a focusing position        of the taking lens;    -   a distance measuring optical system;    -   a distance measuring circuit which detects a distance of an        object for a plurality of points in a photographic screen; and    -   a CPU which receives outputs of at least the image processing        circuit and the distance measuring circuit, and controls the        focus adjustment mechanism based on the received outputs,        determines a distance relation between a main object position        and a background from a plurality of distance measuring results        outputted from the distance measuring circuit, and decides a        control method of the focus adjustment mechanism in accordance        with a result of the determination (corresponding to claim 52).

Advantages of the invention will be set forth in the description whichfollows, and in part will be obvious from the description, or may belearned by practice of the invention. Advantages of the invention may berealized and obtained by means of the instrumentalities and combinationsparticularly pointed out hereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 is a block diagram showing a schematic constitution of an AFcamera according to a first embodiment of the present invention;

FIG. 2 is a perspective view showing an appearance constitution of theAF camera of the first embodiment;

FIG. 3 is a view showing a relation between light receiving lenses 30 a,30 b and sensor arrays 32 a, 32 b, and a taking lens 12 and an imager14;

FIGS. 4A to 4C are views showing an example of focusing when there is anobject on other than a center of a screen;

FIG. 5 is a system block diagram showing a detailed constitution of animage processing section 18 of FIG. 1;

FIG. 6 is a flowchart explaining a photographing operation of the cameraof the first embodiment of the present invention;

FIG. 7 is a flowchart explaining an operation of a camera whencontinuous photographing is carried out in the first embodiment;

FIG. 8 is a view showing a relation between an inverse number 1/L of adistance L and a focusing position LD;

FIGS. 9A to 9C are timing charts showing an effect of a refocusingspeed, FIG. 9A a timing chart when climbing is carried out for eachdistance measuring, FIG. 9B a timing chart in a form of resetting a lensposition for each photographing, and FIG. 9C a timing chart showing aneffect of the first embodiment of the present invention;

FIG. 10 is a block diagram showing a schematic constitution of an AFcamera of a so-called single lens reflex type according to a secondembodiment of the present invention;

FIG. 11 is a perspective view showing an arrangement of a distancemeasuring optical system of FIG. 10;

FIG. 12 is a flowchart explaining a photographing sequence of the cameraof the second embodiment of the present invention;

FIG. 13 is a flowchart explaining an operation of continuousphotographing in the second embodiment;

FIG. 14A is a view showing a state of an optical system when focusing iscarried out by a phase difference AF;

FIG. 14B is a view showing a state of the optical system when a mirroris up;

FIGS. 15A and 15B are views showing an example of a display state of afinder during continuous photographing;

FIG. 16 is a view showing a schematic constitution of an optical systemof an AF camera of a so-called single lens reflex type according to athird embodiment of the present invention;

FIG. 17 is a flowchart explaining a photographing operation of thecamera of the third embodiment of the present invention;

FIGS. 18A and 18B are views showing an example of switching the numberof recording pixels according to a fourth embodiment of the presentinvention;

FIGS. 19A to 19C are views explaining an edge emphasis processingfunction of the fourth embodiment of the present invention;

FIG. 20 is a flowchart explaining a photographing operation of a cameraof the fourth embodiment of the present invention;

FIG. 21 is a block constitutional diagram showing an internalconstitution of a camera of each of fifth and sixth embodiments of thepresent invention;

FIGS. 22A and 22B are views showing the camera and a distance measuringsection of each of the fifth and sixth embodiments, FIG. 22A anexplanatory view showing a principle of the distance measuring sectionincorporated in the camera, and FIG. 22B a perspective view showing anappearance of the camera;

FIGS. 23A and 23B are views showing a photographic scene by the camera,FIG. 23A a view showing a human object in the photographic screen, andFIG. 23B a view showing the human object and a background in thephotographic screen;

FIGS. 24A and 24B are views showing photometry by the camera, FIG. 24Aan explanatory view showing a distance measuring principle of thecamera, and FIG. 24B an explanatory view showing a photometric pointcorresponding to the photographic screen;

FIG. 25 is an explanatory view showing a principle of multidistancemeasuring of an active system;

FIG. 26 is a graph showing a distribution relation between a pluralityof distance measuring points and an object distance;

FIG. 27 is a flowchart explaining a photographing control operation ofthe camera of the fifth embodiment of the present invention;

FIG. 28 is a time chart showing a distance measuring timing, a lensdriving position and a contrast detection timing;

FIG. 29 is a flowchart explaining a photographing control operation ofthe camera of the sixth embodiment of the present invention;

FIG. 30 is a flowchart explaining a photographing control operation of acamera according to a modified example;

FIG. 31 is a flowchart explaining a photographing control operation of acamera according to another modified example;

FIG. 32A is a view showing an example of a scene where a human as a mainobject is present on a screen center;

FIG. 32B is a view showing an example of an image signal obtained by anexternal light distance measuring device which monitors an area 140 a ofa screen 140 of FIG. 32A;

FIG. 32C is a view explaining a change in a monitor position caused byblurring;

FIG. 32D is a view showing an example of an image signal obtained by theexternal light distance measuring device which monitors the area 140 aof FIG. 32C;

FIGS. 33A and 33B are views explaining a distance measuring principle ofan external light distance measuring device which plays an importantrole according to a seventh embodiment;

FIG. 34 is a block diagram showing an internal constitution of a digitalcamera according to the seventh embodiment of the present invention;

FIG. 35A is a view showing a positional relation between light receivinglenses 154 a, 154 b and sensor arrays 156 a, 156 b, and a taking lens160 and an imager 162;

FIG. 35B is an appearance perspective view of the camera of the seventhembodiment;

FIG. 36 is a view showing an example of a distance distribution;

FIG. 37 is a flowchart explaining a distance measuring operation of thecamera of the seventh embodiment of the present invention;

FIG. 38 is a timing chart explaining an operation in the seventhembodiment;

FIG. 39 is a flowchart explaining a distance measuring operation of acamera according to an eighth embodiment of the present invention;

FIG. 40 is a view showing a relation between a focusing position andcontrast;

FIG. 41 is a flowchart explaining a distance measuring operation of acamera according to a modified example of the eighth embodiment of thepresent invention;

FIGS. 42A and 42B are views explaining amounts of blurring at wide timeand tele time by a camera equipped with a zoom, FIG. 42A a view showingthe wide time, and FIG. 42B a view showing the tele time;

FIGS. 43A and 43B are views explaining amounts of blurring at wide timeand tele time by the camera equipped with the zoom, FIG. 43A a viewshowing the wide time, and FIG. 43B a view showing the tele time;

FIG. 44 is a flowchart explaining a distance measuring operation of acamera according to a ninth embodiment of the present invention;

FIG. 45A is a view showing an example of a scene where a human as a mainobject is present in a landscape;

FIG. 45B is a view showing an example of a scene where the human as themain object is present in a situation more disorderly than the scent ofFIG. 45A;

FIG. 45C is a view showing an example of a scene where the main objectis present on an end of a screen;

FIGS. 46A and 46B are views explaining a distance measuring principle ofthe external light distance measuring device which plays an importantrole in the present invention;

FIG. 47 is a view explaining a multidistance measuring device of anactive system;

FIG. 48 is a block diagram showing an internal constitution of a cameraaccording to a tenth embodiment of the present invention;

FIG. 49A is a view showing a positional relation between light receivinglenses 214 a, 214 b and sensor arrays 21 a, 216 b, and a taking lens 220and an imager 222;

FIG. 49B is an appearance perspective view of the camera of the tenthembodiment;

FIG. 50 is a view showing an example of a distance distribution;

FIG. 51 is a flowchart explaining a distance measuring operation of thecamera of the tenth embodiment of the present invention;

FIG. 52 is a timing chart explaining the distance measuring operation ofthe camera of the tenth embodiment;

FIG. 53 is a flowchart explaining a distance measuring operation of acamera according to an eleventh embodiment of the present invention;

FIG. 54 is a flowchart showing a first example of changing step S233 ofdetermination to obtain a difference between a main object distance andanother distance in the flowchart of FIG. 51;

FIG. 55 is a view showing a relation between a focusing paying-outamount and an inverse number 1/L of a distance when focal distances of azoom lens are tele and wide;

FIG. 56 is a flowchart showing a second example of changing the stepS233 of determination to obtain a difference between the main objectdistance and another distance in the flowchart of FIG. 51;

FIG. 57 is a view showing characteristics of image data obtained by asensor array of an external light AF in the scene of FIG. 45A;

FIG. 58A is a view showing characteristics of image data obtained by asensor array of an external light AF in the scene of FIG. 48B;

FIG. 58B is a view showing characteristics of differential data of theimage data of FIG. 58A;

FIG. 59 is a flowchart explaining a distance measuring operation of acamera according to a twelfth embodiment of the present invention;

FIG. 60 is a schematic sectional view showing a constitution of a cameraaccording to a thirteenth embodiment of the present invention; and

FIG. 61 is a view showing an example of a screen 278 of a photometricsensor 266 of FIG. 60.

DETAILED DESCRIPTION OF THE INVENTION

Next, the preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings.

(First Embodiment)

First, description will be made of a first embodiment of the presentinvention with reference to FIGS. 1 to 9C.

FIG. 1 is a block diagram showing a schematic constitution of an AFcamera according to the first embodiment of the present invention.

A light from a main object 10 is passed through a taking lens 12 to forman image on an imager 14 such as a CCD. Then, a signal of the imagesubjected to photoelectric conversion at the imager 14 is outputtedthrough an analog/digital (A/D) converter 16 to an image processingsection 18. The signal processed by the image processing section 18 issupplied to a CPU 20.

The CPU 20 is arithmetic operation control means constituted of amicrocontroller which controls an entire sequence of the camera. The CPU20 comprises a release switch 20 a and a compressibility setting switch20 b described later. The CPU 20 controls a lens driver (LD) 22 forfocusing and controlling the taking lens 12, a recording section 24, andan auxiliary light source 26 such as a flash device. The auxiliary lightsource 26 is used to assist expose or distance measuring in accordancewith a scene.

The light from the main object 10 is entered through a pair of lightreceiving lenses 30 a and 30 b to sensor arrays 32 a and 32 b. Outputsignals from the sensor arrays 32 a and 32 b are supplied through an A/Dconverter 34 and a distance measuring calculation section 36 to the CPU20.

According to such a constitution, when the main object 10 isphotographed, the image formed through the taking lens 12 on the imager14 is electrically converted into an image signal by the imager 14, theA/D converter 16 etc. Then, at the image processing section 18, colorand gradation are adjusted, and the image is compressed to be easilyrecorded in the recording section 24.

Upon detection of an operation of the not-shown release switch 20 a by aphotographer, the image of the main object 10 entered through the lightreceiving lenses 30 a and 30 b is fetched in the sensor arrays 32 a and32 b. Outputs of the sensor arrays 32 a and 32 b are subjected to A/Dconversion at the A/D converter 34, subjected to a digital arithmeticoperation, and a distance to the object is calculated at the distancemeasuring calculation section 36.

After the calculation of the distance, the lens driver 22 is controlledto focus and control the taking lens 12. Subsequently, the image signalfrom the imager 14 is recorded to complete the photographing.

FIG. 2 is a perspective view showing an appearance constitution of theAF camera of the first embodiment.

In FIG. 2, the release switch 20 a and the compressibility settingswitch 20 b are disposed on the upper surface of the camera 40. Thetaking lens 12 is disposed on the center of the front of the camera 40.The light receiving lenses 30 a, 30 b for distance measuring aredisposed above the taking lens 12 and, in FIG. 2, a light emissionwindow 26 a for the auxiliary light source 26 is arranged on the rightside of the light receiving lenses 30 a, 30 b.

A relation between the light receiving lenses 30 a, 30 b and the sensorarrays 32 a, 32 b, and the taking lens 12 and the imager 14 is similarto that shown in FIG. 3.

That is, the same image of the main object 10 can be detected by theexternal light sensor arrays 30 a, 30 b and the imager 14. Additionally,FIG. 3 shows that an object in a position other than the main object 10can also be detected if images of different areas of the sensor arrays30 a, 30 b are utilized.

The external light system AF constituted of the two light receivinglenses and the two sensor arrays is used as in the case of two humaneyes to detect an object distance based on a triangular distancemeasuring principle.

The imager AF detects its contrast by the imager 14 while shifting thefocusing position of the taking lens 12. A lens position of highestcontrast is a position suited to focusing. Thus, the imager AF isbasically different from a system, e.g., the external light AF whichobtains a focusing position based on distance data. That is, even ifthere is an error in lens position control or the like, since thefocusing position including the error is detected, the error is canceledto enable focusing.

However, as shown in FIG. 4A, if the main object 10 is present on otherthan a center of a screen 42, it is difficult to detect presence of thehuman on the front and to quickly focus on this human. It is because ofimpossibility of detecting which main object is present on the frontbefore it is determined that the screen center is great, a focusingposition is examined by focusing on the human (main object) 10, and thenthe taking lens is moved to a tree 44 which becomes a background, and afocusing position is examined by focusing.

If a distance is great between the objects (human 10 and tree 44), ittakes time because a process for stopping the taking lens 12 incorresponding focusing position to fetch images, and to determinecontrast is required.

On the other hand, in the case of the external light system AF, sincedriving of the taking lens is unnecessary, as shown in FIG. 3, it isonly necessary to detect the image of each sensor array, and tocalculate a parallax due to the light receiving lenses 30 a, 30 b. Thus,since a distance distribution can be detected over a wide area 12 cshown in FIG. 4A, a distance distribution of each object can be known,and it is possible to determine where the main object is present and howfar at a high speed.

For example, as shown in FIG. 4B, by obtaining a relation between adistance and a position, it is possible to determine which position andwhat distance of the area 12 c the object is present based on mainobject 10 m data. However, if the image signal is used, since it isdifficult to detect a distance for an area of no contrast of the center,for example, a light may be emitted from the auxiliary light source 26of the camera to detect a reflected light. That is, only a small amountof reflected light is returned from an object of a great distance whilea large amount of a reflected signal light is returned from a neardistance. Thus, for a point which cannot be ranged by the image signal,information is supplemented based on such reflected light amountdetermination. Needless to say, a similar effect can be obtained whennonpresence of the main object in a low contrast area is determined.

Next, a detailed constitution of the image processing section 18 shownin FIG. 1 will be described by referring to a block diagram of FIG. 5.

In FIG. 5, the image processing section 18 is constituted by comprisinga noise reduction circuit 50, a white balance circuit 52, a gamma (γ)correction circuit 54, a color tone correction circuit 56, an RGB/YCconversion circuit 58, and a JPEG compression circuit 60.

The noise reduction circuit 50 removes a noise component from a digitalRGB signal corresponding to three colors A/D converted at the A/Dconverter 16. The white balance circuit 52 carries out processing towhiten a white portion of the image by using the image signal from whichthe noise has been removed.

An output of the white balance circuit 52 is adjusted in brightnesschanging characteristics by the gamma correction circuit 54 of a nextstage in order to naturally represent brightness during displaying on anot-shown monitor or the like. Then, a color tone of a signalcorresponding to three colors RGB is corrected at the color tonecorrection circuit 56.

At the RGB/YC conversion circuit 56, the signal is converted intoluminance information Y, and color difference information C_(b), C_(r)of a color space in order to facilitate compression of a subsequentstage. These obtained Y, Cb, Cr signals are subjected to imagecompression of a JPEG system at the JPEG compression circuit 60. Thisoperation uses the fact that human eyes become insensitive to ahigh-frequency component of an image, and a lower frequency component isquantized more finely while a higher frequency component is quantizedmore roughly. In this case, for example, by a scale factor (parameter),a compressibility, i.e., which frequency component is quantized and howmuch, is changed. This parameter is set based on table data of aparameter setting circuit 62 of the CPU 20 of FIG. 1.

At the CPU 20, an input state (operation state) of the compressibilitysetting switch 20 b is detected to set a compressibility. A recordedimage is rougher as a compressibility is higher while a recorded imageis finer as a compressibility is lower. Accordingly, the number ofimages recorded in the recording section 24 is greatly changed. That is,more images can be recorded as the images are rougher, and the number islower as the images are finer.

For example, a user who goes on a trip or the like only carrying limitedrecording media may wish to capture as many images as possible in thelimited capacity. However, in a scene a fine detail of which isconsidered important, the user may wish to keep an image of a smallcompressibility even if a recording capacity becomes large.

Thus, to reflect a desire to change a compressibility in accordance witha scene, a switch may be disposed in the camera as in the case of theembodiment. The present invention can also be applied to a camera whichdetermines a scene to automatically change compressibility.

Next, description will be made of a photographing operation of thecamera of the first embodiment by referring to a flowchart of FIG. 6.

In the photographing sequence, first, in step S1, distance measuring ofthe external light AF system is carried out. Accordingly, a focusingposition is obtained from an obtained distance L_(H). Then, in step S2,a compressibility is determined in order to switch an operation inaccordance with a set compressibility.

In this system, since there are no feedbacks to the taking lens 12 andthe imager 14 as described above, very small errors are generateddepending on a use environment or a state. However, an influence of theerrors is small in a scene where a high compressibility is allowed.Thus, the process moves to step S3 when a high compressibility is set.

In step S3, a focusing position is decided based on the raging result,and the taking lens 12 is paid out. Then, in step S4, photographing iscarried out.

On the other hand, in step S2, when a compressibility is set small, theuser may wish to reproduce a fine detail. Thus, for focus control, amethod is employed to match even a pixel unit of the imager 14. That is,the process moves from step S2 to step S8, where a paying-out directionof the taking lens 12 for focusing is decided corresponding to thedistance L_(H) in step S1.

Then, in step S9, the taking lens 12 is paid out to the near side by apredetermined position, and climbing AF is executed in step S10 (imagesignal corresponding to an object position obtained during distancemeasuring is used (see FIG. 3)). Here, the taking lens is stopped in aposition where contrast on the imager 14 is highest to carry outfocusing.

Subsequently, photographing is executed in step S11. In step S12, arelation between distance measuring and a lens position is calculatedbased on a focusing position LD_(H) obtained in step S10 and thedistance measuring result of step S1.

After the relation has been calculated, during subsequent photographing,even without executing climbing AF, accurate focusing can be carried outbased on only the distance measuring result.

After the processing of step S4 or S12, in step S5, the aforementionedimage processing is carried out by the image processing section 18.Then, in step S6, JPEG compression is carried out by the JPEGcompression circuit 60 in the image processing section 18 in accordancewith the set compressibility. Then, after image recording in step S7,the sequence is finished.

FIG. 7 is a flowchart explaining an operation of the camera whencontinuous photographing is carried out.

In this case, since the taking lens 12 is repeatedly operated andstopped, even without execution of climbing AF which takes time,external light distance measuring is carried out to obtain a positionand a distance of an object at a high speed in step S21. Then, in stepS22, determination is made based on a compressibility.

If the compressibility is high, the process moves from step S22 to stepS23. In step S23, based on a result of the compressibility, a paying-outdirection of the taking lens 12 is decided as in the case of theflowchart of FIG. 6. On the other hand, if the compressibility is low,the process moves to step S24, where a paying-out position of the takinglens 12 for focusing is decided without executing climbing AF. This isdecided based on the relation between the distance (L) and the focusingposition (LD) calculated in step S12 of the flowchart of FIG. 6. Afterstep S23 or S24, a photographing operation is carried out in step S25.

Processing operations thereafter, i.e., image processing, compressionand image recording of steps S26, S27, S28 are similar to those of stepsS5, 56, S7 described above with reference to the flowchart of FIG. 6,and thus description will be omitted.

In such a flowchart, if even a rough image is satisfactory (e.g., if ascene to be added to electronic mail and finally set in a small-capacityfile is photographed), focusing of a shortened release time lag which isbasic to the camera is carried out.

In the aforementioned example, the user first sets the compressibilityto execute photographing. However, for example, the invention can beapplied to a technology of a system where a camera sets an optimalcompressibility based on an image signal or distance data detected bythe distance measuring sensor array.

For example, in a scene shown in FIG. 4A, a distance distribution shownin FIG. 4B and a color distribution shown in FIG. 4C are obtained. Byusing such information, for example, if a main object is near and itsmage data has a high frequency, a compressibility may be set low.

Next, description will be made of a method which obtains a focusingposition from distance information.

Generally, a relation between an inverse number 1/L of a distance L anda focusing position LD becomes similar to that indicated by a solid linea (examined value) in FIG. 8. Accordingly, the CPU 20 prestores arelation between 1/L and LD represented by the following equation (1):LD=A×1/L+B  (1)

-   -   (A, B are optional numbers).

However, as described above, the relation of the equation (1) is notalways constant because of changes in humidity and temperature and achange of each block by a posture difference. Thus, since a generatederror ΔLD is changed by such conditions, it becomes similar to thatindicated by a broken line b (actual 1) of FIG. 8.

Thus, according to the embodiment, by using an output of the imager in afocusing position LD_(H0) at a distance L_(H) in first distancemeasuring, ΔLD which is a difference from a theoretical value iscalculated by the following equation (2). Based on a result ofre-distance measuring, during focusing of an object of a distance L_(M),the ΔLD is added, and the focus lens is controlled to a focusingposition of LD_(M) by the following equation (3):ΔLD=LD _(H) −LD _(H0)  (2)LD _(M) =A×1/L _(M) +B+ΔLD  (3)

FIGS. 9A to 9C are timing charts showing effects of a refocusing speedin this case.

FIG. 9A is a timing chart when climbing AF is executed for each distancemeasuring. In this case, the taking lens is paid out from an infinite(∞) position in accordance with a distance measuring result. In thedrawing, numerals 1 to 5 indicate five focusing positions, showing asituation of detecting contrast (situation of executing climbing AF).

In second distance measuring, climbing AF is executed again in the fivefocusing positions. In this example, the climbing AF is executed bybringing the focus lens to a climbing start position from the lensposition of the first distance measuring without resetting it.

As shown in the timing chart of FIG. 9B, in the form of resetting thelens position for each photographing, the process takes more timeequivalent to paying-out of an infinite position.

FIG. 9C is a timing chart showing effects of the first embodiment.

According to the present invention, as described above, a focusingposition of the second distance measuring is calculated by using aresult of first lens position (LD) control. Thus, by executing focusingposition control only in distance measuring, focusing is possible withintime of Δt₀. It can be understood that time of Δt₁ is improved comparedwith the example of FIG. 9A, and time of Δt₂ is improved compared withthe example of FIG. 9B.

So-called “backlash” occurs when the lens is withdrawn as shown in FIG.9C. The backlash is inevitable, because the mechanical system moves fora distance when the lens is moved forward and it moves a differentdistance when the lens is withdrawn. The backlash must be considered toset the relation that 1/L and LD should have when the lens is withdrawn.

The relation between 1/L and LD, which has been set in accordance withthe backlash, is indicated by the chain line (c) (actual 2) in FIG. 8.Also shown in FIG. 8 is the relation that 1/L and LD have when the lensis moved forward.

If a difference at the time of the backlash is a predetermined valueΔLD_(B), it can be understood that the lens may be focused on a focusingposition calculated by the following equation (4):LD _(M) =A×1/L _(M) +B+ΔLD−ΔLD _(B)  (4)

Thus, in the timing chart of FIG. 9C, the lens is focused on a positionbased on consideration to the ΔLD_(B) in second focusing. If a result ofsecond distance measuring shows a near distance and it is notaccompanied by a paying-in operation, the calculation of the equation(3) applies.

If the taking lens is a zoom lens, a focusing position is shifted byzooming, and thus focus control is carried out by considering thisshifting.

Such contrivance enables a higher focusing speed to be achieved withoutexecuting climbing AF.

(Second Embodiment)

Next, a second embodiment of the present invention will be described.

FIG. 10 is a block diagram showing a schematic constitution of an AFcamera of a so-called single reflex type according to the secondembodiment of the present invention.

In the embodiment described hereinafter, since a constitution or thelike of the camera is basically similar to that of the first embodiment,similar portions are denoted by similar reference numerals, and drawingsand description thereof will be omitted.

In FIG. 10, a light from a main object 10 is guided through a takinglens 12 to a main mirror 66 which can be rotated in an arrow direction Cin the drawing, and which is constituted of a half mirror. If this mainmirror 66 is retreated (positioned above) from an optical path, thelight from the main object 10 forms an image on an imager 14. On theother hand, if the main mirror 66 is positioned in the optical path, thelight from the main object 10 is reflected by the main mirror 66 to forman image on a focusing screen 67. Further, through a pentaprism 70 andan eyepiece lens 72, the formed image can be observed by an eye 74 of aphotographer.

Such optical constitutional contrivance enables checking of a videopassed through the taking lens 12.

A liquid crystal display section 76 and an illumination section 78 aredisposed through a driver 75 before the pentaprism 70 to form anelectronic video by the imager 14.

On the other hand, as shown in FIG. 11, the object image passed throughthe main mirror 66 is reflected by a submirror 80 disposed after themain mirror 66. Then, the object image is formed through a condenserlens 82, a mirror 84 and a separator lens 86 on a photodiode array 88.

This image corresponds to a different pupil position of the taking lens12, and a pair of image signals are formed for one point in the screen.The pair of image signals are set in a predetermined positional relationwhen the camera is focused on the object. Thus, in focus control of thetaking lens 12 by the CPU 20, the taking lens 12 for focusing is movedback and forth through a lens driver 22 so as to set positions of thepair of image signals in a predetermined positional relation (TTL phasedifference AF).

If the submirror 80 is constituted of a half mirror, a part of a mainincident light on the imager 14 by the taking lens 12 reaches above theimager 14 even if the main mirror 66 is located in the optical path.Accordingly, image processing is carried out at an image processingsection 18 to extract a contrast signal, and the taking lens 12 isfine-adjusted to enable execution of climbing AF. That is, according tothe second embodiment, AF of the two systems can be used in combinationas in the case of the first embodiment. However, during photographing,in the retreated state of the main mirror 66 from the optical pathbetween the taking lens 12 and the imager 14, the TTL phase differenceAF cannot be executed.

A liquid crystal display section 76 and the illumination section 78disposed before the pentaprism 70 constitute an electronic finder (EVF).This electronic finder enables continuous monitoring of an electronicimage made incident on the imager 14 from the taking lens 12 even if theimage from the taking lens 12 is not projected on the focusing screen 68after the main mirror 66 is retreated out of the optical path.

Thus, different from the case of the conventional single lens reflexcamera, a field of vision is not blacked out even while a shutter isopen.

By such contrivance, photographing can be enjoyed in long-time exposureor for a moving body while a movement of an object is checked.

FIG. 12 is a flowchart explaining a photographing sequence of the cameraof the second embodiment.

In the sequence, first, in step S31, focusing is carried out by theaforementioned phase difference system. Normally, this focusingsuffices. However, among a group of users of single lens reflex cameras,many set great store by image quality. Thus, in such a case, ifphotographing is carried out by low image compression, fine adjustmentis added by climbing AF which evaluates contrast by a pixel unit of theimager.

Thus, in subsequent step S32, a compressibility is determined. Ifphotographing of a low compressibility is selected, the process moves tostep S33. If photographing of a high compressibility is selected, theprocess moves to step S34.

In step S33, in addition to the focusing by the phase difference, fineadjustment by climbing AF is added to carry out photographing by higherresolution.

Subsequently, in step S34, the main mirror 66 is retreated out of theoptical path (mirror up), and photographing is executed in subsequentstep S35. Then, after the main mirror 66 is positioned in the opticalpath (mirror down) in step S36, image processing is carried out in stepS37. Further, image compression processing of step S38, and imagerecording of step S39 are carried out to finish the sequence.

In this case, the aforementioned electronic finder function may beactuated to enable checking of the object image even while the mirror isup as shown in FIG. 14B.

During continuous photographing, the EVF function can be used moreeffectively.

FIG. 13 is a flowchart explaining the continuous photographingoperation.

First, as in the case of the flowchart of FIG. 12, focusing by a phasedifference AF is carried out in step S41. At this time, the main mirror66 is located in a position shown in FIG. 14A.

Then, the mirror is moved up in step S42, and a compressibility isdetermined in step S43.

If photographing of a low compressibility is selected, the process movesto step S44 to execute climbing AF. On the other hand, in the case ofphotographing of a high compressibility, the process moves to step S45.Then, photographing is executed in step S45.

Then, in step S46, an image picked up by moving the mirror up isdisplayed by this timing as shown in FIG. 14B, and displayed on themonitor in the finder to function the electronic finder.

After image processing of step S47, image compression processing ofsubsequent step S48 and image recording of step S49 are carried out.Subsequently, in step S50, focusing is executed by climbing AF.Accordingly, second photographing is carried out in step S51. In theexecution of this photographing, image processing is carried out againin step S52, and image compression processing of step S53 and imagerecording of step S54 are carried out.

Then, in step S55, determination is made as to whether the continuousphotographing is finished or not. If the photographing (continuousphotographing) is not finished yet, the process moves to step S50. Iffinished, the process moves to step S56.

In step S56, the monitor displaying in the finder which functions as theelectronic finder in step S46 is turned OFF. Then, the mirror is moveddown in step S57 to finish the sequence.

Steps S47 to S49 are steps of image processing, compression andrecording. However, if the main mirror is moved up and down for eachphotographing, a time lag is made longer. Thus, during the continuousphotographing, after the mirror is moved up in step S42, the mirror isnot moved down (step S57) until the end of the continuous photographing(step S55).

After step S50, no phase difference AF is carried out, focusing iscarried out by climbing AF, and the photographing sequence of steps S51to 54 is repeated. The finder at this time is different from an opticalfinder (OVF) shown in FIG. 15A, and a display form (EVF) shown in FIG.15B may be employed.

In the example shown in FIG. 15B, only the main object is enlarged sothat a human expression can be known well. The monitor displaying inthis finder is turned OFF before the mirror is moved down to suppresscurrent consumption. However, roughness of a pixel during displaying maybe switched to check effects.

As described above, according to the second embodiment of the presentinvention, in the digital camera of the so-called single lens reflextype, the AF system can be selected which is designed to set balancebetween a time lag basic to the camera and resolution by effectivelyusing the TTL phase difference AF and the climbing AF separately.

(Third Embodiment)

Next, a third embodiment of the present invention will be described.

As an optical system of a single lens reflex camera, a constitution isnot limited to that described above with reference to FIG. 10, but aconstitution similar to that of FIG. 16 may be employed.

That is, as shown in FIG. 16, the camera constitution of the secondembodiment may be simplified by forming a phase difference AF sensor 88on the same chip as that of an imager 14 for imaging.

The second embodiment has been described only by way of switching basedon a compressibility. According to the third embodiment, however, a timelag priority mode can be set as shown in a flowchart of FIG. 17.

FIG. 17 is a flowchart explaining a photographing operation of a cameraof the third embodiment.

First, in step S61, determination is made as to whether a time lagpriority mode is selected or not. If the time lag mode is selected, theprocess moves to step S62 to carry out phase difference AF. Then, duringphotographing of step S63, a compressibility of photographing data isset high to record the data.

If the time lag priority mode is not selected in step S61, the processmoves to step S64 to determine a compressibility. If a compressibilityis not low, the process moves to step S65 to carry out phase differenceAF. Then, in step S66, contrast is checked.

If a result of the checking shows that the contrast is equal to/higherthan predetermined contrast, the process moves to step S63 to startphotographing, and recording is carried out at high compression. On theother hand, if the contrast is lower than the predetermined contrast instep S66, the process moves to step S67 to carry out climbing AF, andthen the process moves to step S63 to carry out photographing andrecording.

If photographing where high resolution is obtained to lower acompressibility is determined in step S64, the process moves to step S68to carry out phase difference AF first. Subsequently, climbing AF iscarried out in step S69. In this case, a compressibility is lowered whenphotographing and recording are carried out in step S70.

Thus, according to the third embodiment, the AF system is decided byconsidering the release time lag and the compressibility.

(Fourth Embodiment)

Next, a fourth embodiment of the present invention will be described.

The first to third embodiments have been described by paying attentionto the compressibility. However, according to the concept of the presentinvention, the AF system may be switched in accordance with not only thecompressibility but also other parameters which decide image quality.

For example, a digital camera incorporates processing which converts animage constituted of a pixel shown in FIG. 18A into a pixel of an arealarger by four times shown in FIG. 18B (switching of the number ofrecording pixels). The digital camera often incorporates an edgeemphasis processing function which detects, for an image pattern similarto that shown in FIG. 19A, an edge of a black and white changing pointas shown in FIG. 19B, and increases a gain of this portion to add it toan original image (see FIG. 19C). In accordance with such processingselection, the AF system of the camera may be switched as shown in aflowchart of FIG. 20.

FIG. 20 is a flowchart explaining a photographing operation of a cameraof the fourth embodiment of the present invention.

That is, first, in step S271, determination is made as to whether a zoomposition is tele (T) or not. If the zoom position is tele, the processmoves to step S272. If not, the process moves to step S273.

First, in step S81, phase difference AF is carried out (e.g., externallight AF in the constitution of FIG. 1). Then, in step S82,determination is made as to whether the number of pixels is small ornot. If the number of pixels is small, the process moves to step S83,and to step S85 if otherwise.

Then, in step S83, determination is made as to whether edge emphasis iscarried out or not. In the case of edge emphasis, the process moves tostep S84, and to step S86 if otherwise.

In step S84, contrast is determined. If a result shows that the contrastis equal to/higher than predetermined contrast, the process moves tostep S86, and to step S85 if lower. In step S85, climbing AF is carriedout.

That is, if the number of pixels is small and no edge emphasis iscarried out, photographing, image processing and image recording ofsteps S86, S87, S88 are directly carried out. On the other hand, if thenumber of pixels is large, irrespective of edge emphasis, climbing AF ofstep S85 is carried out in addition to phase difference AF of step S81.

If edge emphasis is carried out while the number of pixels is small,contrast is determined in step S84. If a result shows that the contrastis equal to/higher than the predetermined contrast, the process directlystarts photographing of step S86. If lower than the predeterminedcontrast, climbing AF of step S85 is executed.

Thus, according to the fourth embodiment, the AF system is optimizedbased on the number and sizes of pixels of an image, execution ofsharpness processing etc. That is, for a sharp photograph having a largenumber of pixels, climbing AF which considers even contrast of a pixelunit is carried out. For other photographs, however, since a time lag ismade longer in this system, no climbing AF is carried out, andhigh-speed focusing is achieved.

According to the first to fourth embodiments, it is possible to providea camera which optimizes a relation between a focus control system and acompressibility to combine them, and sets balance between a release timelag and a memory amount of an image recording medium.

Next, brief description will be made of a basic constitution and anoperation of a camera according to each of fifth and sixth embodimentswith reference to FIGS. 21 to 23B.

FIG. 21 is a block constitutional view showing an internal constitutionof the camera of each of the fifth and sixth embodiments of the presentinvention. FIGS. 22A and 22B are views schematically showing anappearance of the camera and a distance measuring section inside. FIGS.23A and 23B are views showing an example of a scene to be photographedby the camera.

As shown in FIG. 21, the camera is constituted by including amicroprocessor (CPU) 100, a pair of light receiving lenses 102 a, 102 b,a pair of sensor arrays 104 a, 104 b, a distance measuring section 106constituted of an A/D conversion section 106 a, a distance measuringcalculation section 106 b etc., a taking lens 110, an imager 112, an A/Dconverter 114, an image processing section 116, a lens driving section118, a zoom detection section 120, a recording medium 122, and a lightsource 124 as an auxiliary light source. This is a camera of a typecalled an external light system AF (referred to as “external light AF”hereinafter).

The CPU 100 works as arithmetic operation control means to control aphotographing sequence (detailed later) of the entire camera overall. Aswitch 100 a which starts the photographing sequence is connected to theCPU 100. According to setting, when the CPU 100 recognizes an ONoperation of the switch 100 by a not-shown photographer, a series ofphotographing operations are started. The CPU 100 includes a function aslater-described selection means, and controls the camera to select aplurality of focusing functions based on a position of an object imagein a photographic screen (detailed later).

The pair of light receiving lenses 102 a, 102 b are arranged to receivea reflected light from an object 130, and to form images on the pair ofsensor arrays 104 a, 104 b. In the pair of sensor arrays 104 a, 104 b,formed images (object images) from the object 130 are converted intoelectric signals (referred to as “image signals” hereinafter) to beoutputted to the distance measuring section 106.

The distance measuring section 106 is distance measuring means of a“passive system” constituted by including the A/D conversion section 106a and the distance measuring calculation section 106 b. The A/Dconversion section 106 a in the distance measuring section 106 convertsthe image signals entered from the sensor arrays 104 a, 104 b intodigital signals, and outputs them to the distance measuring calculationsection 106 b. The distance measuring calculation section 106 bcalculates a distance (object distance) from the camera to the objectbased on the digital signals by a “triangular distance measuringprinciple”. The distance measuring section 106 is equivalent to adistance measuring device incorporated in the camera.

The CPU 100 carries out focusing control of the taking lens 110 based onthe calculated object distance. That is, the CPU 100 focuses the takinglens 110 by controlling the lens driving section 118 based on the objectdistance calculated by the distance measuring calculation section 106 b.

The imager 112 is constituted of a CCD or the like. After the end of thefocusing of the taking lens 110, this CCD is used to carry out anelectronic exposure operation. That is, the imager 112 converts theobject image formed through the taking lens 110 into an electric imagesignal, and outputs it to the analog/digital (A/D) converter 114.

The A/D converter 114 converts the image signal into a digital signal,and then outputs the digital signal to the image processing section 116.At the image processing section 116, color and gradation of the imageare corrected based on the entered digital signal, then compressionprocessing is executed for a corresponding image signal, the image isrecorded on the recording medium 122, and thus a series of exposureoperations are completed.

The light source 124 is constituted of a flash device or the like. Fromthe light source 124, an auxiliary light for exposure or distancemeasuring is radiated to the object 130 in accordance with a scene to bephotographed as occasion demands.

A positional relation between the light receiving lenses 102 a, 102 band the sensor arrays 104 a, 104 b, and the taking lens 110 and theimager 112 is similar to that shown in FIG. 22A. The same image of theobject 130 can be detected by the sensor arrays 104 a, 104 b and theimager 112.

Specifically, when outputs of the sensor arrays 104 a, 104 b are usedfor calculation of an object distance, in place of an image of theobject 130 formed in a position indicated by a solid line in thedrawing, an image of the object 130 formed in a different position,e.g., a position indicated by a broken line in the drawing, is used.Accordingly, it is possible to detect distances of objects other thanthe object 130 in the photographic screen (see a plurality of distancemeasuring points: FIG. 26B).

In the photographic screen, as actual examples, a center human 130 a asa main object similar to that shown in FIG. 23A, and a backgroundincluding a human 130 a on a peripheral end and a center building 130 bas a background object similar to that shown in FIG. 23B can bephotographed.

Thus, the distance measuring section 106 incorporated in the camerawhich has an appearance similar to that shown in FIG. 22B carries out adistance measuring operation of a predetermined external light systembased on the arrangement of the components shown in FIG. 22A.

A release button 100 b is projected from the upper surface of thecameral (main body) 132 on the appearance to operate the switch 100 a.On the front of the camera 132, the taking lens 110 and the lightreceiving lenses 102 a, 102 b are arranged in the positional relationshown in FIG. 22A. Further, a light emission window 124 a for the lightsource 124 of the incorporated flash device is disposed on the upper endof the front of the camera 132.

Thus, it can be said that the camera of the embodiment is mainlyconstituted of components which have the following functions.

That is, the camera comprises contrast detection means (imager 112, A/Dconverter 114 or the like) which detects contrast of an object imagesignal obtained through the taking lens 110, multipoint distancemeasuring means (distance measuring section 106) which ranges aplurality of points in the photographic screen through a pair of opticalsystems (light receiving lenses 102 a, 102 b or the like) different fromthe taking lens 110, first, second focus adjustment means (lens drivingsection 118) which focus the taking lens 110 based on a detection resultof the contrast detection means or a distance measuring result of themultipoint distance measuring means, position determination means(sensor arrays 104 a, 104 b) which determines a position of a mainobject in the photographic screen, and the CPU 100 which operates thefirst focus adjustment means (a part of the lens driving section 118)when the position determination means determines that the main object ispositioned on the center, and which operates the second focus adjustmentmeans (a part of the lens driving section 118) when the main object isdetermined to be positioned on the periphery in the photographic screen.

Next, features will be described by way of the fifth and sixthembodiments.

(Fifth Embodiment)

Hereinafter, description will be made of features of the camera of thefifth embodiment with reference to FIGS. 23A and 23B.

Regarding “scene division” for focusing control intended by aphotographer in the composition of the photographic screen, a sceneshown in FIG. 23A is an example where a human 130 a as a main object ison the center of the screen, and a scene shown in FIG. 23B is an examplewhere the human 130 a as the main object is on the periphery of thescreen.

In the case of FIG. 23A, since the human 130 a is on a most importantposition of the screen, there is no doubt that a main object of thenot-shown photographer is this human 130 a. Thus, since sufficient focuscontrol is considered necessary for the human 130 a, focusing is carriedout by an “imager AF” which is not affected by a temperature, a humidityand a posture difference during photographing. The imager AF is a systemto determine contrast of an image while moving the taking lens 110, andthus it has a drawback that it takes time to start/stop the taking lens110 and a time lag is made longer.

The focusing of such a system is not always satisfactory in a scenesimilar to that of FIG. 23B. That is, in such a scene to bephotographed, the photographer is surely interested not only in thehuman 130 a but also in the background building 130 b, and thephotographer may wish to focus not only on the human 130 a but also onthe building 130 b. Such a situation is often generated during trips,snapshot photographing is not a target itself, rather a value as arecord of memories is high, and the photographing is normally finishedwithin a short time.

In such a scene to be photographed, there is no problem even if thecamera is focused on the background, e.g., the building 130 b. Even ifthere is a slight error in the lens driving control as described above,as long as it is little far from the human 130 a, the error can often beignored.

Under such a situation, if time is taken more than necessary to focus onthe human 130 a, a photo opportunity may often be lost. It is all rightif a background object is stationary. However, as shown in FIG. 23B, ina scene where a ship sails across or the like, if focusing takesexcessive time, the ship may goes out of the screen 134. Thus, undersuch a photographing scene, in the camera of the fifth embodiment of theinvention, especially focusing which sets great store by a speed havingpriority on time is carried out.

Now, description will be made of distance measuring in the camera, i.e.,a distance measuring principle of the external light distance measuringdevice which plays an important role in the present invention byreferring to FIGS. 24A and 24B.

FIG. 24A schematically shows the distance measuring principle of thecamera, and FIG. 24B shows an arrangement example of photometry pointscorresponding to the photographic screen.

The image of the object 130 is guided to the sensor arrays 104 a, 104 bby the pair of light receiving lenses 102 a, 102 b separated from eachother by a base line length between focal distances. An obtained lightfrom the object forms an image of a relative position difference x wherean optical axis is an origin in accordance with a triangular distancemeasuring principle. Then, an object distance L is obtained based on therelative position difference x.

FIG. 24A shows an example where an image on the optical axis of thelight receiving lens 102 a is made incident on a position x (positionshifted by x from the center) on the sensor array 104 b. In the case ofdistance measuring a position shifted by θ from the optical axis of thelight receiving lens 102 a, if a focal distance of the light receivinglens is f, by using an image signal of a position ftan θ, a distance upto a point shifted from the optical axis is obtained by a similar idea(L=f/x).

Thus, since several distance measuring points can be set in the arrayingdirection of the sensor arrays 102 a, 102 b, as shown in FIG. 24B, it ispossible to obtain object distance data regarding multiple points in thescreen (multidistance measuring). The distance measuring device havingsuch a distance measuring function is called a “multipoint distancemeasuring device”.

The multidistance measuring device of the “active system” which is awell-known technology may be used in the embodiment. For example, asshown in a principle of active system multidistance measuring of FIG.25, lights from a plurality of LED's 136 are projected through aprojection lens 102 c, and reflected signal lights thereof are receivedthrough a light receiving lens 102 d by an optical position detector 138to examine incident positions. In this way, multidistance measuringsimilar to the above can be carried out.

As described above, in the external light system AF (external light AF)described above with reference to FIGS. 21, 22A and 22B, by using thepair of light receiving lenses 102 a, 102 b and the pair of sensorarrays 104 a, 104 b similarly to both eyes of the human, an objectdistance is detected based on the triangular distance measuringprinciple, and the taking lens 110 is focused based on the objectdistance.

On the other hand, in the AF (imager AF) which uses the imager outputthrough the taking lens 110, contrast of an object image formed on theimager 112 is detected while the position of the taking lens 110 ischanged by the lens driving section 118. Then, the position of thetaking lens 110 where contrast becomes highest is determined to be setas a focusing position (lens position of a focusing point).

That is, the imager AF carries out focus control which is different fromthe system which decides a focusing position based on the objectdistance as in the case of the external light AF.

In such an imager AF, even if an error is generated in the positioncontrol of the taking lens 110, it is possible to detect a focusingposition by considering an error as long as the error is small.

However, as shown in FIG. 23B, if the human 130 a as the main object islocated on other than the center of the photographic screen 134, it isdifficult to quickly focus the taking lens 110 on the human 130 a.

That is, in order to specify the main object, after contrastdetermination is carried out for each of the human 130 and thebackground building 130 b as described above, it is necessary todetermine which of the human 130 a and the background (e.g., building130 b) is suitable as a main object, e.g., which object is located moreon the front side. In such a case, it is necessary to carry out theprocess of contrast determination after an image in a focusing positioncorresponding to each object is temporarily fetched, which makes timerelatively longer.

In the “external light A”, image signals from the sensor arrays 104 a,104 b shown in FIG. 22A are detected, and shifting of the image signalsof the objects based on the parallax of the light receiving lenses 102a, 102 b is detected to decide object distances. That is, since the timeof driving the taking lens 110 is only after the focusing position isdecided, time necessary for focusing is made shorter compared with thatof the imager AF.

For a distance to an object other than the main object, it is onlynecessary to switch the image signal of the object used in objectdistance calculation. Thus, irrespective of the position of the mainobject, it is possible to detect an object distance distribution in awide area such as an area 104 c shown in FIG. 24B.

FIG. 26 is a graph showing an example of the detected distancedistribution. That is, an ordinate indicates a distance, and fivedistance measuring points are plotted in an abscissa.

After the distance distribution is obtained, where the main object islocated can be detected at a high speed. In this case, since right endone of the five distance measuring points is located relatively near,its detection target can be surmised to be a main object.

Next, specific description will be made of operation control of thecamera based on a basic idea of the present invention.

FIG. 27 is a flowchart explaining a control operation regarding“photographing” in the camera of the fifth embodiment.

First, in step S91, the distance measuring device of the external lightAF is driven to range multipoints in the screen. Then, in step S92,since a distance distribution (see FIG. 26) is obtained in a scenesimilar to that of FIG. 23B, for example, a nearest distance is selectedas a main object distance L from this distribution.

In step S93, determination is made as to whether a point (i.e., mainobject position) indicating a nearest distance is on the center of thephotographic screen 134 or not. If the point is on other than thecenter, the process moves to step S94. For example, in a scene similarto that of FIG. 23B, the operation is regarded as snapshotphotographing, and quick focusing which gives priority to a speed iscarried out.

In the case of such a scene, photographing including a backgroundbecomes a problem more than “just focusing” on a human. Accordingly, ifthe taking lens 110 is focused accurately on the distance L of thehuman, shifting caused by an error of lens control to focus on a neardistance side results in a photograph of no focus. Thus, a possibleerror is added, and lens control for focusing is carried out so as tofocus on a far distance side (∞ side) from the distance L. Then, theprocess directly moves to step S99, where a photographing operation isexecuted, and a series of photographing operations are finished.

Such contrivance enables photographing where focus balance is setbetween the human and the background at a high speed.

On the other hand, in a scene similar to that shown in FIG. 23A, a mainobject is located on the center of the screen 134 and, different fromthe case of FIG. 23B, it is considered that an interest of thephotographer is not in the background but only in the human 130 a. Insuch a case, since just focusing on the human 130 a becomes one of theconditions for producing a good photograph, the sequence of the imagerAF which can set a state of “just focusing” including a lens error iscontinuously carried out.

However, if contrast detection is executed for all the areas of lensdriving, it leads to a great time loss. Accordingly, in step S95, thetaking lens 110 is driven before a lens position equivalent to thedistance L to the object. Then, in step S96, contrast detection isstarted.

Then, in step S97, a lens position where contrast is maximum isdetected. Here, until the position of the maximum contrast is found, theprocess moves to step S98, where the lens position is finely adjusted tosearch a position of “just focusing”. Then, focus is set on thisposition and, after correct focusing, the process moves to step S99 tostart a photographing operation. After the end of the photographingoperation, the routine is finished.

According to the embodiment based on the foregoing scene division, inthe scene where the interest of the photographer is concentrated on oneobject (human) as shown in FIG. 23A, careful focusing on the human iscarried out even if it takes time. In the scene of snapshotphotographing during a trip as shown in FIG. 23B, focus control whichgives priority to a speed is carried out, and thus no photo opportunityis lost.

FIG. 28 shows three timing charts of matched time series for a distancemeasuring timing, and detection timings of a lens driving (LD) positionand contrast for reference.

First, distance measuring is carried out by the external light systemdistance measuring device and, subsequently, lens driving control isexecuted based on a result thereof. For example, in a scene similar tothat of FIG. 23A, contrast detection is further carried out here, and alens position of peak contrast is obtained. Thus, lens driving andcontrast detection are repeated for time Δt.

However, in a scene similar to that of FIG. 23B, the above contrastdetection is not carried out. Thus, photographing can be started withintime shorter by Δt. However, even in the composition of FIG. 23B, inorder to just focus on the human, photographing is carried out by usinga well-known “focus lock” technology or the like.

For example, in the camera which has a focus lock button (not shown) forexecuting well-known focus lock control before photographing, when thefocus lock button is operated, focusing based on contrast of an imagesignal obtained through the taking lens 110 is not carried out.

On the other hand, a camera is implemented which has a feature that whenthe focus lock button is not operated, focus control means (lens drivingsection 118, CPU 100 or the like) is set so as to carry out focusingbased on an output result of distance measuring by an optical system(light receiving lenses 102 a, 102 b) different from the taking lens110.

As described above, according to the fifth embodiment, when the focuslock is operated, considering that the photographer as a user intends tofocus even if it takes time, photographing which gives priority to focusaccuracy is carried out. On the other hand, when the object is locatedon the periphery of the screen, photographing based on the externallight AF which gives priority to time is carried out so as not to lose aphoto opportunity. In this external light AF, after lens driving basedon an object distance obtained as a result of external light distancemeasuring is executed, focus is set on a desired object in thecomposition to carry out photographing. Thus, it is possible to enjoyphotographing in accordance with a photographing situation and aphotographing scene.

(Sixth Embodiment)

Next, description will be made of the sixth embodiment as anotherimprovement example of the present invention.

The camera is a zoom camera which includes basic components similar tothose of the foregoing camera (see FIG. 21).

Hereinafter, a photographing control operation of the camera of thesixth embodiment will be described by referring to a flowchart of FIG.29, a principle view of an active multidistance measuring of FIG. 25,and a graph of FIG. 26 showing a distribution relation between aplurality of distance measuring points and an object distance.

According to the sixth embodiment, “zoom position determination” of stepS101 regarding the taking lens 110 is added to the flowchart of FIG. 27.The embodiment provides a long focal distance. For example, theembodiment is effective for a camera equipped with a zoom lens.

That is, in the zoom lens of long focus, a slight error of lens drivingduring focusing results in a large error to adversely affect photocoming-out itself. In a photographing scene using such a zoom lens,control is carried out to give priority to the imager AF.

In the scene of the composition shown in FIG. 23B, since there is a wishto enter many landscapes in the photographic screen 134, considerationis given to the fact that photographing is often carried out on the wideangle side of the zoom lens. Thus, by considering the zoom position ofthe lens and the object position, a photographing scene which givespriority to a photo opportunity such as snapshot photographing isdetermined to execute focusing.

Thus, in the camera of the sixth embodiment, by using the zoom detectionsection 120 (see FIG. 21), photographing is carried out in a controlprocedure shown in the flowchart of FIG. 29.

First, in step S101, a zoom position of the zoom lens is determined.Subsequently, in step S102, multipoint distance measuring is carried outby external light distance measuring. Further, in step S103, a distancedistribution of distance measuring points is created based on valuesobtained by the distance measuring.

Then, in step S104, an object distance L to a main object is determinedfrom the form of the distance distribution. In this case, however,different from the fifth embodiment, it is not always necessary toregard an object of a nearest distance as a main object. For example, aselection method which has “predetermined distance priority” or ignoresan object too near as a “rough object” may be implemented, to which thepresent invention can be applied.

In step S105, determination is made as to a position of the obtainedmain object in the screen. For example, if the position of the mainobject is on the periphery of the photographic screen, the process movesto step S106, and to step S107 if the position is not on the periphery.

In step S106, determination is made as to a zoom position. Here, if thezoom position is on the wide side, the process moves to step S108, wherea flag indicating execution or nonexecution of the imager AF is set to“0”. In the case of other conditions (standard, telescopic), the processmoves to step S107, where the flag indicating execution or nonexecutionof the imager AF is set to “1”.

In subsequent step S109, the lens is shifted to the ∞ side (far distanceside) from the main object distance L obtained in step S104 by an errorconceivable in lens control to carry out focusing. Then, in step S110,determination is made as to whether the flag indicating execution ornonexecution of the imager AF is “1” or not. If the flag is other than“1”, the process moves to step S114, where a high-speed electronicphotographing operation is started without operating the imager AF.

On the other hand, in step S110, if the flag indicating execution ornonexecution of the imager AF is “1”, the imager AF which can executefeedback control considering even a lens stop position error is started.That is, in step S111, the image obtained through the taking lens 110 isused to start contrast detection. Then, in step S112, a size of theimage contrast is determined.

In this case, until maximum image contrast is determined, the processmoves to step S113, where the taking lens 110 is moved only by a smallamount to be finely adjusted, and the contrast detection is repeated. Ina position where the contrast of the obtained image becomes maximum, thelens driving (LD) is stopped, and the process moves to step S114 tostart an electronic photographing operation. Then, the photographing isfinished.

As described above, according to the sixth embodiment, the camera havingthe zoom lens in the taking lens 110 comprises the multipoint distancemeasuring means (distance measuring section 106) which measuresdistances to the objects of the plurality of points in the photographicscreen by the optical system (light receiving lenses 102 a, 102 b)different from the taking lens 110, the contrast focusing means (lensdriving section 118 for the zoom lens) which decides a focusing positionbased on the contrast of the photographing target obtained through thetaking lens 110, the zoom detection means (zoom detection section 120)which detects the zoom position of the taking lens 110, and the decidingmeans (CPU 100) which decides whether or not to actuate the contrastfocusing means in accordance with the zoom position and the result ofthe multipoint distance measuring.

As control regarding scene division, determination processing of thezoom position of the taking lens is added, a high possibility ofsnapshot photographing is understood when the zoom position is on thewide side, and focusing which gives priority to a speed is carried out.However, if the main object is on the center of the photographic screen,or during photographing in a telescopic state, control is carried out toexecute photographing which gives priority to focusing accuracy.

Thus, an optimal focusing method can be selected by adding the zoomposition and automatically determining a photographing situation.Therefore, an easy-to-use camera can be provided.

MODIFIED EXAMPLE

The fifth and sixth embodiments may be modified as follows.

For example, the present invention can be applied to a camera which canuse a focus lock in combination.

FIGS. 30 and 31 are flowcharts explaining in detail a photographingcontrol operation of the camera of the modified example. As in theprevious case, according to the modified example, a release button 100 bis coupled with a two-stage release switch which corresponds to firstand second release switches. Distance measuring can be carried out by anON operation of the first-stage switch corresponding to the firstrelease switch, and electronic photographing can be carried out bydepressing until the second-stage switch is turned ON. In this example,especially, if photographing is carried out by changing a compositionafter a focusing position is decided at the first stage, focus lockingis enabled.

FIG. 30 is a flowchart explaining a control operation when the focuslocking is possible. That is, in the camera which additionally includesa focus lock switch (not shown), specification of the followingflowchart can be designed.

First, in step S121, presence of an operation of the focus lock switchis detected. Then, if the focus lock switch is operated, the processmoves to step S122, where careful focusing is carried out by the imagerAF, and then photographing of step S124 is started.

On the other hand, if the focus lock switch is not operated, the processmoves to step S123, where external light AF is carried out. In stepS123, focusing is executed only based on a result of the external lightAF. Then, the process moves to step S124 to start photographing.

FIG. 31 is a flowchart more specifically showing the aforementionedprocess.

Specifically, first, in step S131, determination is made as to an ONoperation (half depressing) of the first stage of the two-stage releaseswitch. If the ON operation is detected, in subsequent step S132,distances to distance measuring points are measured by “external lightmultidistance measuring”.

Based on a result of the distance measuring, in step S133, determinationis made as to whether a distance to a point corresponding to the screencenter is a nearest object distance or not. If the screen center isdetermined not to be a nearest object distance, the process moves tostep S134.

On the other hand, if the point corresponding to the screen center isdetermined to be a nearest object distance, the process moves to stepS135 to operate the imager AF. Then, in subsequent step S136, displayingregarding the focus locking is executed.

In step S134, determination is made as to continuance of the ON state ofthe first release switch for a predetermined time before the releasebutton is depressed to turn ON the second release switch. If the ONstate of the first release switch is continued, the process moves tostep S135, and to step S137 if not.

In step S137, determination is made as to an ON state of the secondrelease switch. Here, during focus locking, the composition is changedbefore the second release switch is turned ON, and the process movesfrom S138 to S139.

The user continues an ON operation of the first release switch until afocus lock display is outputted in step S136.

After one execution of the imager AF, in step S139, determination ismade as to the end of the imager AF. If the end is determined, theprocess moves again to step S137. Thus, the process waits for releasebutton depressing determination of step S137, and moves to aphotographing sequence of next step S140 by a release button operationof the user by a photographing timing.

By such a modified example, effects similar to those of the fifth andsixth embodiments can be expected.

The present invention can be similarly applied to a camera which has amultipoint distance measuring function even if it is other than thecamera which uses the foregoing electronic imager.

(Seventh Embodiment)

Next, the seventh embodiment of the present invention will be described.

First, the seventh embodiment will be described briefly by referring toFIGS. 32A to 32D.

FIG. 32A shows a scene where a human as a main object is located on ascreen center, and FIG. 32B shows an example of an image signal obtainedby an external light system distance measuring device which monitors anarea 140 a of a screen 140 of FIG. 32A.

In FIG. 32A, if the camera is firmly held by a photographer, and nochanges occur even if an image signal is repeatedly detected, there isno doubt that a main object is a human 142 a in the screen 140. Thus,sufficient focusing control is considered necessary for the human 142 a,and focusing is carried out by an imager AF which is not affected by atemperature, humidity or a posture change.

However, since image contrast is determined while a lens is moved, theimager AF has a drawback that it takes time to start/stop the lens, andthus a time lag is made longer. Focusing of such a type is not alwaysnecessary in a scene where image changes occur.

That is, as shown in FIG. 32C, a change in a monitoring position causedby blurring in hasty photographing (see arrow E in the drawing) causesan image change similar to that shown in FIG. 32D. However, in such asituation, the photographer may start photographing in a hurry,photographing which gives priority to a time lag is preferred and, inthe imager AF, a disturbed change similarly occurs in a contrast valueby an image change. Thus, it is a scene of difficult focusing.

Such a situation often occurs during trips or the like, photographing ishigher in value as a record of memories than a target, and it should becarried out within a short time. Additionally, in such a scene,instantaneous expression of the object is more important than focusing.Even if there is an error in lens driving control (LD) as describedabove, the error can be ignored as long as expression and overallatmosphere can be reproduced.

In such a situation, if time more than necessary is taken to focus onthe human, needless to say, a photo opportunity is lost. It is all rightin a landscape where a background is stationary. However, for example,as shown in FIG. 32C, in a scene where a ship 142 b sails across in thebackground or the like, if excessive time is taken for focusing, theship 142 b may go out of the screen. Thus, in a situation similar tothat shown in FIG. 32C, according to the present invention, focusingwhich gives priority to time is carried out.

Next, description will be made of a distance measuring principle of theexternal light system distance measuring device which plays an importantrole in the embodiment by referring to FIGS. 33A and 33B.

In FIG. 33A, a pair of light receiving lenses 144 a, 144 b are arrangedin positions separated from the object 142 by a distance L. A distancebetween main points thereof is equal to a base line length B, and thelight receiving lenses 144 a, 144 b guide images of the object 142 tosensor arrays 146 a, 146 b. A light thus obtained from the object 142forms an image having a relative position difference x where an opticalaxis is an origin based on a triangular distance measuring principle. Adistance L is obtained from x.

In FIG. 33A, an image on the optical axis of the light receiving lens144 a is made incident on the x position of the sensor array 146 b.However, in the case of distance measuring a position shifted from theoptical axis of the light receiving lens 144 a by θ, if a focal distanceof the light receiving lens is f, by using an image signal of a positionftan θ, a distance of a point shifted from the optical axis can beobtained by a similar idea (L=Bf/x).

Thus, since several distance measuring points can be set in the arrayingdirection of the sensor arrays, as shown in FIG. 33B, distance data ofseveral points 148 in the screen can be obtained. A distance measuringdevice having such a function is called a multipoint distance measuringdevice. Since it is external light distance measuring, even if zoomingchanges the screen to T (tele: telescopic)/W (wide: wide angle), thedistance measuring sensor monitors the same place.

Next, the seventh embodiment of the present invention will be described.

FIG. 34 is a block diagram showing an internal constitution of thecamera of the seventh embodiment of the present invention.

In FIG. 34, the digital camera is constituted by including amicroprocessor (CPU) 152, a pair of light receiving lenses 154 a, 154 b,a pair of sensor arrays 156 a, 156 b, a distance measuring section 158,a taking lens 160, an imager 162, an analog/digital (A/D) converter 164,an image processing section 166, a lens driving section 168, a zoomdetection section 170, a recording medium 172, and a light source 174.

The CPU 152 works as arithmetic operation control means to control anoverall sequence of the camera, and includes selection means and controlmeans. A switch 152 a which starts the photographing sequence isconnected to the CPU 152. The CPU 152 determines an ON operation of theswitch 152 a by a photographer to start a series of photographingoperations.

The pair of light receiving lenses 154 a, 154 b receive an image from anobject 150, and form images on the pair of sensor arrays 156 a, 156 b.In the pair of sensor arrays 156 a, 156 b, formed images (object images)from the object 150 are converted into electric signals (referred to as“image signals” hereinafter) to be outputted to the distance measuringsection 158.

The distance measuring section 158 is distance measuring means of apassive system constituted by including the A/D conversion section 158 aand a distance measuring calculation section 158 b. The A/D conversionsection 158 a in the distance measuring section 158 converts the imagesignals entered from the sensor arrays 156 a, 156 b into digitalsignals, and outputs them to the distance measuring calculation section158 b. The distance measuring calculation section 158 b calculates adistance, i.e., object distance, from the camera to the object 150 basedon the digital signals by the aforementioned triangular distancemeasuring principle. The distance measuring section 158 is equivalent toa distance measuring device.

The CPU 152 carries out focusing control of the taking lens 160 based onthe calculated object distance. That is, the CPU 152 focuses the takinglens 160 by controlling the lens driving (LD) section 168 based on theobject distance calculated by the distance measuring calculation section158 b.

The zoom detection section 170 is zoom position detection means whichdetects a zoom position of the taking lens 160. The zoom detectionsection 170 detects how much the taking lens 160 is moved on the opticalaxis by the lens driving section 168, i.e., the zoom position. Thus, theCPU 152 carries out focusing in accordance with the zoom positionobtained by the zoom detection section 170 and the image signal from thedistance measuring section 158.

After the end of the focusing of the taking lens 160, an exposureoperation is carried out. The imager 162 is constituted of a CCD or thelike. The image of the object 150 formed through the taking lens 160 isconverted into an electric image signal, and outputted to the A/Dconverter 164. The imager 162 is equivalent to an “imager”.

The A/D converter 164 converts the image signal from the imager 162 intoa digital signal, and then outputs the digital signal to the imageprocessing section 166. At the image processing section 166, color andgradation of the image are corrected based on the entered digitalsignal, then compression is executed for an image signal. Then, thecompressed image is recorded on the recording medium 172, and thus theexposure operation is completed.

The light source 174 is constituted of a flash device or the like. Fromthe light source 174, an auxiliary light or the like for exposure ordistance measuring is radiated to the object 150 in accordance with ascene to be photographed.

A positional relation between the light receiving lenses 154 a, 154 band the sensor arrays 156 a, 156 b, and the taking lens 160 and theimager 162 is similar to that shown in FIG. 35A.

That is, the same image of the object 150 can be detected by the sensorarrays 156 a, 156 b and the imager 162. When outputs of the sensorarrays 156 a, 156 b are used for object distance calculation, by usingan image of an object formed in a different position, e.g., a positionindicated by a broken line in the drawing, in place of the image of theobject 150 formed in the position indicated by a solid line in thedrawing, as shown in FIG. 33B, it is possible to detect distances ofobjects other than the object 142 in the photographic screen.

FIG. 35B is an appearance perspective view of the camera of the seventhembodiment.

In FIG. 35B, a release button 152 b is disposed on the upper surface ofthe camera 180 to operate the switch 152 a. The taking lens 160 isdisposed nearly on the center of the screen of the camera 180. The lightreceiving lenses 154 a, 154 b are arranged above the taking lens 160 inthe positional relation shown in FIG. 35A. Further, in FIG. 35B, a lightemission window 174 a for the light source 174 is disposed on the rightside of the light receiving lenses 154 a, 154 b.

In the aforementioned external light system AF, by using the pair oflight receiving lenses 154 a, 154 b and the pair of sensor arrays 156 a,156 b similarly to both eyes of the human, an object distance isdetected based on the triangular distance measuring principle, and thetaking lens 160 is focused based on the object distance.

On the other hand, the AF which uses the imager output through thetaking lens 160 is called an imager AF. This imager AF detects contrastof an object image formed on the imager 162 while changing the positionof the taking lens 160, and determines a position of the taking lens 160where contrast becomes highest to set it as a focusing position.

That is, the imager AF carries out focus control which is different fromthe system which decides a focusing position based on the objectdistance as in the case of the external light AF.

In such an imager AF, even if an error is generated in the positioncontrol of the taking lens 160, it is possible to detect a focusingposition by considering an error as long as the error is small. As shownin FIG. 32A, if the human 142 a as the main object is located on thecenter of the photographic screen 140, there is no problem. However, ifthe human 142 a is located on other than the center of the photographicscreen 140, it is difficult to quickly focus the taking lens 160 on thehuman 142 a.

That is, in order to specify the main object, after contrastdetermination is carried out for each of the human 142 a and thebuilding as a background object, it is necessary to determine which ofthe objects is suitable as a main object, e.g., which object is locatedmore on the front side. In such a case, it is necessary to carry out theprocess of contrast determination after an image in a focusing positioncorresponding to each object is temporarily fetched, which makes timerelatively longer.

On the other hand, in the external light AF, image signals from thesensor arrays 156 a, 156 b shown in FIG. 35A are detected, and shiftingof the image signals of the objects based on the parallax of the lightreceiving lenses 154 a, 154 b is detected to decide object distances.That is, since the time of driving the taking lens 160 is only after thefocusing position is decided, time necessary for focusing is madeshorter compared with that of the imager AF.

For a distance to an object other than the main object, it is onlynecessary to switch the image signal of the object used in objectdistance calculation. Thus, irrespective of the position of the mainobject, it is possible to detect an object distance distribution in awide area such as an area 148 shown in FIG. 33B.

FIG. 36 is a view showing an example of the obtained distancedistribution.

After the distance distribution is obtained, where the main object islocated can be detected at a high speed.

Next, description will be made of a distance measuring operation of thecamera of the seventh embodiment by referring to a flowchart of FIG. 37.

In step S151, an image signal is detected by the external light distancemeasuring device to range a plurality of points in the screen. Whendistances are obtained as a result, a distribution similar to that shownin FIG. 36 is obtained for a scene shown in FIG. 33B. Thus, in stepS152, a nearest distance is selected as a main object distance.

In subsequent step S153, image detection is carried out again to detectan image which is a feature of the embodiment.

Then, in step S154, determination is made as to whether there is anychange in the image signal obtained by a plurality of image detections.If there is an image signal, the process moves to step S155. Then, forexample, in a scene similar to that shown in FIG. 32C, the operation isregarded as snapshot photographing, and focusing which gives priority toa speed is carried out. In such a scene, instantaneous expression or thelike of the human becomes a problem more than just focusing on thehuman.

As described above, the scene determination is carried out based onpresence of blurring caused by camera holding during photographing. Thatis, in a scene to be accurately focused, the user firmly holds thecamera, and takes time to photograph the object. On the other hand, insnapshot photographing during trips or the like, blurring easily occursbecause the release button is quickly operated. In this case, theblurring is detected by an image change. After the processing of stepS155, the process directly moves to step S160 to photograph the object,and the operation is finished.

However, in a scene similar to those shown in FIGS. 32A and 32B, thereis no change in the image of the main object 142 a and, different fromthe scene of FIG. 31C, an interest of the photographer may beconcentrated on only human representation. In this case, since justfocusing on the human is one of the conditions to produce goodphotographs, the sequence of the imager AF which can realize a justfocused state including a lens error is continued. However, if contrastdetection is executed for all the lens driving areas, it leads to agreat time loss. Thus, in step S156, the lens is driven before the lensposition equivalent to the main object distance L, and contrastdetection is started in step S157.

Then, in step S158, a lens position of maximum contrast is detected.Here, if contrast is not maximum, the process moves to step S159 tofinely adjust the lens position, and moves to step S157. That is, theprocess of steps S157 to S159 is repeated until the position of maximumcontrast is found, and a position of just focusing is searched.

Thus, if the contrast is maximum in step S158, the process moves to stepS160, where focus is set on its position to execute photographing.

As described above, according to the embodiment, as shown in FIG. 31A,in the scene where the interest of the photographer is concentrated onlyon one object (human), focus is set on the human even if it takes time.As shown in FIG. 32C, in the scene of snapshot photographing duringtrips or the like, since focusing which gives priority to a speed iscarried out, a photo opportunity is not lost.

FIG. 38 is a timing chart explaining an operation of the seventhembodiment.

First, distance measuring by the external light system distancemeasuring device is carried out and, based on the result thereof, lenscontrol (LD) is carried out. In the scene shown in FIG. 32A, contrastdetection is further executed to obtain a lens position of peakcontrast. Thus, the lens control and the contrast detection are repeated(At period).

However, in the scene shown in FIG. 32C, the above contrast detection isnot executed. Thus, photographing can be started within a time shorterby Δt. Additionally, if even in the composition shown in FIG. 32B, focusis set on the human, photographing may be carried out by using awell-known focus locking technology or the like.

Next, an eighth embodiment of the present invention will be described.

FIG. 39 is a flowchart explaining a distance measuring operation of acamera of the eighth embodiment of the present invention.

According to the eight embodiment, as described above, during the imagerAF of contrast detection which takes time, image detection is repeatedby using the sensor array of repeated external light distance measuring,and generation of blurring or an image data change caused by a movementof an object is monitored.

By switching determination based on a zoom position, more specificsituation determination is carried out. That is, consideration is givento the fact that the number of snapshot photographing times is larger ata wide time than at a tele time, a time lag should be made shorter, anda large focal depth prevents a photo from becoming out of focus becauseof a slight lens stop error.

On the assumption of such points, first, a zoom position is determinedin step S171. Then, an image for distance measuring is detected in stepS172, and a main object distance L is obtained in step S173. Then, instep S174, lens driving is executed so as to focus on a side little farfrom the distance L. Additionally, since blurring may occur even at thisstage, image detection is carried out again in step S175.

Then, in step S176, the image detection results of steps S171 and 5175are compared with each other. In this case, if there is an image change,a zoom position is determined in subsequent step S177. That is, in stepsS176 and S177, if there is an image change and the zoom position iswide, the process moves to step S178, where focus control is carried outto focus on the distance L obtained in step S173. This means thatphotographing is started without any time for the photographer to firmlyhold the camera, and focusing which gives importance to a timing iscarried out. Then, the process moves to step S183 to executephotographing.

On the other hand, if the zoom lens is tele even when there is an imagechange, a lens position error often affects focusing conspicuously.Thus, the process moves to step S179 to start contrast detection. Evenwhen no image change is detected on the wide in step S178, the processalso moves to step S179.

Upon detection of a lens position of maximum contrast in step S180, theprocess moves to step S183 to execute photographing.

Thus, since image detection is carried out in step S182 for each fineadjustment of the taking lens position of step S181, and the processmoves to step S176, if blurring or object shaking occurs during theexecution of the imager AF, the process moves to step S178 to starthigh-speed focusing by the external light AF. On the other hand, if thezoom position is tele, the imager AF which deals with a lens positionerror is continued as described above.

As described above, according to the eighth embodiment, a photographingscene is determined more accurately in accordance with blurring, objectshaking and a zoom position, and a focal depth by the zoom position isadded to implement an optimal focusing system. Thus, it is possible toprovide an AF camera which can reduce stress on the photographer bypreventing a loss of a photo opportunity and an out-of focus state.

The imager AF carries out focusing by using a change in contrast(contrast is higher as the lens is focused more) with respect to thefocusing amount LD of the taking lens. However, it is on the assumptionthat an area is monitored through the taking lens by the imager. If thearea is changed due to blurring or the like, correct focus controlcannot be executed.

For example, as shown in FIG. 40, it is assumed that no blurring occurswhen contrast is determined at focusing positions LD₁, LD₂ (point e inthe drawing). Even if contrast is higher at LD₃, when a monitoringposition is changed by blurring to cause a change in an incident image(point f in the drawing), it is erroneously determined that contrast isstopped, and the lens position of LD₂ is a best focusing position.

In order to deal with such a situation, determination is made by theexternal light distance measuring device as to whether an objectposition monitored by the imager is changed or not to determinecontrast. When there is an optional change (blurring), contrastdetermination is carried out all over again. The process is shown in aflowchart of FIG. 41.

FIG. 41 is a flowchart explaining a distance measuring operation of acamera according to a modified example of the eighth embodiment of thepresent invention.

First, in step S191, image detection is carried out by the externallight distance measuring device. Based on a result thereof, a mainobject distance L is obtained in step S192. Then, in step S93, a focuslens is controlled to a focusing position thereof. Further, in stepS194, image detection is carried out again by the external lightdistance measuring sensor in step S194.

Then, in step S195, a level of an image change is switched based on thezoom position of the taking lens. Specifically, a determination level attele time is set small since an influence is larger at the tele timeeven in the case of the same amount of blurring.

Then, in step S196, the image changes detected in step S191 and stepS194 are compared with each other. If a result shows a large imagechange, considering that the scene is improper for the imager AF, theprocess moves to step S204 to immediately start photographing.

However, if an image signal is not greatly changed, in steps S197 toS199, contrast detection is executed while lens driving (LD) is carriedout by a small amount. Then, in step S200, image detection is carriedout by the external light sensor.

In step S201, the image changes are compared again. If a result showsthat an image change is equal to/lower than a predetermined value (abouta middle level), the process moves to step S202 to detect contrast.Then, the process of steps S198 to S202 is repeated until contrastbecomes maximum. When the contrast becomes maximum, the les driving isfinished, and the process moves to step S104 to start photographing.

On the other hand, in step S201, if the image change is detected by theexternal light sensor, it is determined that blurring has caused achange in monitoring position. Thus, the process moves to step S203 tocalculate a distance L again. Then, in step S193, the process is startedall over again from focusing position control.

Thus, since the imager AF can be carried out from a position whereblurring has stopped, it is possible to execute highly accuratefocusing. Moreover, even if the blurring is not stopped, in step S196,the process is branched to carry out focusing which gives priority to aspeed.

Therefore, according to the embodiment, a scene in which the imager AFis unskilled is detected by the external light sensor to enable highlyaccurate AF.

In the case of a camera equipped with a zoom, as shown in FIGS. 42A and42B, a near-distance object is often photographed on the wide, and afar-distance object on the tele. In this case, if the same blurringamount θ_(b) occurs, an image is detected on a face of the object at thewide time shown in FIG. 42A, but an image detection area may be shiftedfrom the face at the tele time shown in FIG. 42B.

In such a state, correct focusing is difficult in the imager AF whichrepeats detection many times. This is because the blurring amount θb ofan area 182 at the wide time shown in FIG. 43A is greatly changed in thescreen at the tele time as shown in FIG. 43B.

Thus, external light distance measuring can be preferentially carriedout on the telescopic side or a far-distance side.

A ninth embodiment of the present invention is directed to a cameradistance measuring which gives priority to external light distancemeasuring on a telescopic side or a far-distance side.

FIG. 44 is a flowchart explaining a distance measuring operation of thecamera of the ninth embodiment of the present invention.

First, in step S211, a distance l is obtained by external light distancemeasuring. In subsequent step S212, a focal distance f is obtained byzoom position detection. In accordance with a result thereof, focusingby external light distance measuring or focusing by an imager AF isselected.

That is, in step S213, the focal distance f obtained in step S212 iscompared with a predetermined focal distance f₁. If the focal distance fis determined to be larger than the focal distance f₁, the externallight AF is selected to proceed to step S219. On the other hand, if f isequal to/smaller than f₁, the process moves to step S214.

In step S214, the focal distance f is compared with f₀ which is smallerthan the focal distance f₁. If a result shows that f is larger than f₀,the process moves to step S215. If f is equal to/smaller than f₀, theprocess moves to step S216.

In step S215, the distance L obtained in step S211 is compared with apredetermined distance L_(T). If L is nearer than L_(T), the processmoves to step S217. If it is farther, the process moves to step S219.

On the other hand, in step S216, the distance L obtained in step S211 iscompared with a predetermined distance L_(W). If L is nearer than L_(W),the process moves to step S217. If it is farther, the process moves tostep S219.

In the case of a near distance, the imager AF is selected. That is, insteps S217 and S218, the taking lens is driven to a position equivalentto the distance L, and focusing is executed by the imager AF.

In the case of a far distance, the process moves to step S219, andfocusing is executed on the distance by external light distancemeasuring.

Then, photographing is executed in step S220.

Thus, according to the ninth embodiment, it is possible to carry outaccurate focusing which predicts an influence of blurring, and reducesthe influence of blurring.

The seventh to ninth embodiments have been described by way of exampleof the digital camera. However, the invention is not limited to this,and various changes can be made without departing from the teachings.For example, needless to say, the invention can be applied to a portabletelephone, a PDA etc., having imaging sections other than the digitalcamera.

Next, the tenth embodiment will be described briefly with reference toFIGS. 45A to 45C.

FIG. 45A shows an example of a scene where a human as a main object islocated in a landscape, FIG. 45B shows an example of a scene where thehuman as the main object is located in a situation rougher than that ofthe scene of FIG. 45A, and FIG. 45C shows an example of a scene wherethe main object is located on an end of the screen.

In the case of the scene shown in FIG. 45A, since a distance of anobject is completely separated from the landscape on a screen 190, thereis no doubt that a main object of a photographer is a human 192 a. Thus,sufficient focusing control is considered necessary for the human 192 a,and focusing is carried out by an imager AF which is not affected by atemperature, humidity or a posture change.

However, since image contrast is determined while a lens is moved, theimager AF has a drawback that it takes time to start/stop the lens, andthus a time lag is made longer. Focusing of such a type is not alwaysnecessary in a scene similar to that shown in FIG. 45B.

That is, in such a scene, the photographer is surely interested not onlyin one human but also other humans and a background. Thus, it may be ascene where the photographer wishes to focus not only on the human 192 abut also on a human 192 b, a background 192 c etc. Such a situationoften occurs at parties, banquets or the like, photographing is higherin value as a record of memories than a target, and it should be carriedout within a short time. Additionally, in such a scene, focusing on anear background is not a problem, and even if there is an error in lensdriving control (LD) as described above, the error can often be ignoredas long as it is located a little far side from the human.

In such a situation, if time more than necessary is taken to focus onthe human, a photo opportunity is often lost. It is all right in alandscape or the like where a background is stationary. However, forexample, as shown in FIG. 45B, in a scene where there are a plurality ofhumans, if excessive time is taken for focusing, gestures, expressionsetc., of all the humans may go out of the intension of the photographer.

Thus, in a situation similar to that shown in FIG. 45B, according to theembodiment, focusing which gives priority to time is carried out.

Next, description will be made of a distance measuring principle of theexternal light system distance measuring device which plays an importantrole in the present invention by referring to FIGS. 46A and 46B.

In FIG. 46A, a pair of light receiving lenses 194 a, 194 b are arrangedin positions separated from the object 192 by a distance L. A distancebetween main points thereof is equal to a base line length B, and thelight receiving lenses 194 a, 194 b guide images of the object 192 tosensor arrays 196 a, 196 b. A light thus obtained from the object 192forms an image having a relative position difference x where an opticalaxis is an origin based on a triangular distance measuring principle. Adistance L is obtained from x.

In FIG. 46A, an image on the optical axis of the light receiving lens194 a is made incident on the x position of the sensor array 196 b.However, in the case of distance measuring a position shifted from theoptical axis of the light receiving lens 194 a by θ, if a focal distanceof the light receiving lens is f, by using an image signal of a positionftan θ, a distance of a point shifted from the optical axis can beobtained by a similar idea (L=Bf/x).

Thus, since several distance measuring points can be set in the arrayingdirection of the sensor arrays, as shown in FIG. 46B, distance data ofseveral points 198 in the screen can be obtained. A distance measuringdevice having such a function is called a multipoint distance measuringdevice.

As the multipoint distance measuring device, a well-known active systemmultidistance measuring device may be used. For example, as shown inFIG. 47, a plurality of LED's 194 d project lights through a projectionlens 194 c, and reflected signal lights thereof are received through alight receiving lens 194 d by an optical position detector 202 toinvestigate incident positions thereof. Similar multidistance measuringcan be carried out in this way.

Next, the tenth embodiment of the present invention will be described.

FIG. 48 is a block diagram showing an internal constitution of thecamera of the tenth embodiment of the present invention.

In FIG. 48, the digital camera of the tenth embodiment of the inventionis constituted by including a microprocessor (CPU) 212, a pair of lightreceiving lenses 214 a, 214 b, a pair of sensor arrays 216 a, 216 b, adistance measuring section 218, a taking lens 220, an imager 222, ananalog/digital (A/D) converter 224, an image processing section 226, alens driving (LD) section 228, a zoom detection section 230, a recordingmedium 232, and a light source 234.

The CPU 212 works as arithmetic operation control means to control anoverall sequence of the camera, and includes selection means and controlmeans. A switch 212 a which starts the photographing sequence isconnected to the CPU 212. The CPU 212 determines an ON operation of theswitch 212 a by a photographer to start a series of photographingoperations.

The pair of light receiving lenses 214 a, 214 b receive an image from anobject 210, and form images on the pair of sensor arrays 216 a, 216 b.In the pair of sensor arrays 216 a, 216 b, formed images from the object210 are converted into electric signals (referred to as “image signals”hereinafter) to be outputted to the distance measuring section 218.

The distance measuring section 218 is distance measuring means of apassive system constituted by including an A/D conversion section 218 aand a distance measuring calculation section 218 b. The A/D conversionsection 218 a in the distance measuring section 218 converts the imagesignals entered from the sensor arrays 216 a, 216 b into digitalsignals, and outputs them to the distance measuring calculation section218 b. The distance measuring calculation section 218 b calculates adistance, i.e., object distance, from the camera to the object 210 basedon the digital signals by the aforementioned triangular distancemeasuring principle. The distance measuring section 218 is equivalent toa “distance measuring device”.

The CPU 212 carries out focusing control of the taking lens 220 based onthe calculated object distance. That is, the CPU 212 focuses the takinglens 220 by controlling the lens driving section 228 based on the objectdistance calculated by the distance measuring calculation section 218 b.

The zoom detection section 230 is zoom position detection means whichdetects a zoom position of the taking lens 220. The zoom detectionsection 230 detects how much the taking lens 220 is moved on the opticalaxis by the lens driving section 228, i.e., the zoom position. Thus, theCPU 212 carries out focusing in accordance with the zoom positionobtained by the zoom detection section 230 and the image signal from thedistance measuring section 218.

After the end of the focusing of the taking lens 220, an exposureoperation is carried out. The imager 222 is constituted of a CCD or thelike. The image of the object 210 formed through the taking lens 220 isconverted into an electric image signal, and outputted to the A/Dconverter 224. The imager 222 is equivalent to an “imager”.

The A/D converter 224 converts the image signal from the imager 222 intoa digital signal, and then outputs the digital signal to the imageprocessing section 226. At the image processing section 226, color andgradation of the image are corrected based on the entered digitalsignal, then compression is executed for an image signal. Then, thecompressed image is recorded on the recording medium 232, and thus theexposure operation is completed.

The light source 234 is constituted of a flash device or the like. Fromthe light source 234, an auxiliary light or the like for exposure ordistance measuring is radiated to the object 210 in accordance with ascene to be photographed.

A positional relation between the light receiving lenses 214 a, 214 band the sensor arrays 216 a, 216 b, and the taking lens 220 and theimager 222 is similar to that shown in FIG. 49A.

That is, the same image of the object 210 can be detected by the sensorarrays 216 a, 216 b and the imager 222. When outputs of the sensorarrays 216 a, 216 b are used for object distance calculation, by usingan image of an object formed in a different position, e.g., a positionindicated by a broken line in the drawing, in place of the image of theobject 210 formed in the position indicated by a solid line in thedrawing, as shown in FIG. 46B, it is possible to detect distances ofobjects other than the object 192 in the photographic screen.

FIG. 49B is an appearance perspective view of the camera of the tenthembodiment.

In FIG. 49B, a release button 212 b is disposed on the upper surface ofthe camera 240 to operate the switch 212 a. The taking lens 220 isdisposed nearly on the center of the screen of the camera 240. The lightreceiving lenses 214 a, 214 b are arranged above the taking lens 220 inthe positional relation shown in FIG. 49A. Further, in FIG. 49B, a lightemission window 234 a for the light source 234 is disposed on the rightside of the light receiving lenses 214 a, 214 b.

In the aforementioned external light system AF, by using the pair oflight receiving lenses 214 a, 214 b and the pair of sensor arrays 216 a,216 b similarly to both eyes of the human, an object distance isdetected based on the triangular distance measuring principle, and thetaking lens 220 is focused based on the object distance.

On the other hand, the AF which uses the imager output through thetaking lens 220 is called an imager AF. This imager AF detects contrastof an object image formed on the imager 222 while changing the positionof the taking lens 220 by the lens driving section, and determines aposition of the taking lens 220 where contrast becomes highest to set itas a focusing position.

That is, the imager AF carries out focus control based on a principledifferent from the system which decides a focusing position based on theobject distance as in the case of the external light AF.

In such an imager AF, even if an error is generated in the positioncontrol of the taking lens 220, it is possible to detect a focusingposition by considering an error as long as the error is small. However,as shown in FIG. 45C, if the human 192 a as a main object is located onother than the center of the photographic screen 190, it is difficult toquickly focus the taking lens 220 on the human 192 a. In this case, thecenter of the photographic screen is a building 192 d which becomes abackground object.

That is, in order to specify the main object, after contrastdetermination is carried out for each of the human 192 a and thebuilding 192 d, it is necessary to determine which of the objects issuitable as a main object, e.g., which object is located more on thefront side. In such a case, it is necessary to carry out the process ofcontrast determination after an image in a focusing positioncorresponding to each object is temporarily fetched, which makes timerelatively longer.

On the other hand, in the external light AF, image signals from thesensor arrays 216 a, 216 b shown in FIG. 49A are detected, and shiftingof the image signals of the objects based on the parallax of the lightreceiving lenses 214 a, 214 b is detected to decide object distances.That is, since the time of driving the taking lens 220 is only after thefocusing position is decided, time necessary for focusing is madeshorter compared with that of the imager AF.

For a distance to an object other than the main object, it is onlynecessary to switch the image signal of the object used in objectdistance calculation. Thus, irrespective of the position of the mainobject, it is possible to detect an object distance distribution in awide area such as an area 198 shown in FIG. 46B.

FIG. 50 is a view showing an example of the obtained distancedistribution.

After the distance distribution is obtained, where the main object (g inthe drawing) is located can be detected at a high speed.

Next, description will be made of an operation of the tenth embodimentby referring to a flowchart of FIG. 51.

First, in step S231, a plurality of points in the screen are ranged bythe external light distance measuring device. For example, adistribution similar to that shown in FIG. 50 is obtained for a sceneshown in FIG. 45B. Thus, in step S232, a nearest distance is selected asa main object distance L.

In subsequent step S233, determination is made as to whether adifference between a point (main object position) indicating a nearestdistance and the other point is large or not. Here, if the difference issmall, the process moves to step S234, where for example in a scenesimilar to that shown in FIG. 45B, the operation is regarded as snapshotphotographing, and focusing which gives priority to a speed is carriedout. In such a scene, coming-out of a photograph including thebackground becomes a problem more than just focusing on the human.

Additionally, in the scene of FIG. 45B, there are objects before thehuman, and these objects are also important to the photographerdepending on situations. Thus, considering that only human focusing isnot always important, focusing which gives priority to a timing ratherthan a slight error is carried out. Then, the process moves to step S239to finish the photographing.

On the other hand, if the difference is large in step S233, the processmoves to step S235. In the scene shown in FIG. 45A, a distance of themain object 192 a is greatly different from the background. That is,different from the case of the scene shown in FIG. 45B, an interest ofthe photographer is not in the background but concentrated on only thehuman. In such a case, since just focusing on the human is one of theconditions to produce good photographs, the sequence of the imager AFwhich can realize a just focused state including a lens error iscontinued.

However, if contrast detection is executed for all the lens drivingareas, it leads to a great time loss. Thus, in step S235, the lens isdriven (LD) before the lens position equivalent to the main objectdistance L, and contrast detection is started in step S236.

Then, in step S237, a lens position of maximum contrast is detected.Here, if contrast is not maximum, the process moves to step S238 tofinely adjust the lens position, and a position of just focusing issearched.

The process of steps S236 to S238 is repeated until the position of themaximum contrast is found. After the position of the maximum contrast isreached, focus is set on this position to execute photographing in stepS239.

As described above, according to the tenth embodiment, as shown in FIG.45A, in the scene where the interest of the photographer is concentratedonly on one object (human), focus is set on the human even if it takestime. As shown in FIG. 45B, in the scene of snapshot photographing atparties or banquets, since focusing which gives priority to a speed iscarried out, a photo opportunity is not lost.

FIG. 52 is a timing chart explaining a distance measuring operation ofthe camera of the tenth embodiment.

First, distance measuring by the external light system distancemeasuring device is carried out and, based on the result thereof, lenscontrol (LD) is carried out. In the scene shown in FIG. 45A, contrastdetection is further executed to obtain a lens position of peakcontrast. Thus, the lens control and the contrast detection are repeated(At period).

However, in the scene shown in FIG. 45B, the above contrast detection isnot executed. Thus, photographing can be started within a time shorterby Δt. Additionally, if even in the composition shown in FIG. 45B, focusis set on the human, photographing may be carried out by using awell-known focus locking technology or the like.

Next, an eleventh embodiment of the present invention will be described.

According to the eleventh embodiment, zoom position determination of ataking lens is added to the flowchart of FIG. 51. The embodiment iseffective for a camera equipped with a long focal distance zoom lens.

That is, in the zoom lens of long focus, a slight error of lens drivingduring focusing results in a large error to adversely affect photocoming-out. In such a photographing scene, priority is given to theimager AF. In a scene similar to that shown in FIG. 45B, since there isa wish to enter many such as a background, and a surrounding atmospherein the photographic screen, consideration is given to the fact thatphotographing is often carried out on the wide angle side of the zoomlens. Thus, by considering the zoom position of the lens and the objectposition, a photographing scene which gives priority to a photoopportunity such as snapshot photographing is determined to executefocusing.

Now, description will be made of a distance measuring operation of acamera according to a twelfth embodiment of the present invention byreferring to a flowchart of FIG. 53.

First, in step S241, a zoom position is determined by using a zoomdetection section 230 as shown in FIG. 48. Subsequently, in step S242,multipoint distance measuring is carried out by external light distancemeasuring. Thus, a distance distribution is obtained in subsequent stepS243, and a main object distance L is determined in step S244.

However, different from the case of the twelfth embodiment, it is notalways necessary to regard an object of a nearest distance as a mainobject. A selection method which has predetermined distance priority orignores an object too near as a rough object may be implemented, towhich the present invention can be applied.

Then, variance in inverse numbers of the distances of the points isobtained. Since this variance can be determined based on standarddeviation a or the like, the standard deviation a is compared withanother in step S245.

If small σ is determined, the process moves to step S246 to determinewhether the zoom position is on the wide side or not. If a resultthereof shows that the zoom position is on the wide side, the processmoves to step S247, where a flag for implementing the imager AF is setto 0. On the other hand, if the standard deviation σ is determined notto be small in step S245 or the zoom position is determined not to be onthe wide side in step S246, the process moves to step S248, where theflag for implementing the imager AF is set to 1.

Then, in step S249, the lens is shifted to the ∞ side (far distanceside) from the main object distance L obtained in step S244 by an errorconceivable in lens control to carry out focusing, and thus an importantbackground is taken into consideration. Then, in step S250,determination is made as to a flag (imager flag) for implementing theimager AF.

If the flag is other than “1”, the process moves to step S254, wherehigh-speed photographing is started without operating the imager AF.However, if the flag for implementing the imager AF is “1”, a sequenceof the imager AF which can execute feedback control considering even alens stop position error is started.

That is, in step S251, the image obtained through the taking lens isused to start contrast detection. Then, in step S252, if an image ofmaximum contrast is not determined, the process moves to step S253 tomove the lens by a very small amount, and then the process moves to stepS251. That is, until maximum image contrast is determined, contrastdetection is repeated in steps S250 to S253.

At a point where the contrast of the obtained image becomes maximum, thelens driving (LD) is stopped, and the process moves to step S254 toexecute photographing.

As described above, according to the twelfth embodiment, the zoomposition of the taking lens is added and, if the zoom position is on thewide side, considering that a possibility of snapshot photographing ishigh, focusing which gives priority to a speed is carried out. However,if the main object is far from the background or in a telescopic state,photographing which gives important to focusing accuracy is carried out.

Thus, according to the twelfth embodiment, it is possible to provide aneasy-to-use camera which can select an optimal focusing method by addingthe zoom position and automatically determining a photographingsituation.

In the flowchart of FIG. 53, the variance in distances of the objects isdetermined by using the standard deviation. However, the determinationstep of obtaining a difference between the main object distance and theother distance in the flowchart of FIG. 15 may be changed to analgorithm similar to that shown in FIG. 54. Here, an example of addingzoom information to the determination method is described.

Generally, a focusing paying-out amount and an inverse number 1/L of adistance are set in a proportional relation similar to that shown inFIG. 55. However, between the telescopic (tele) case and the wide caseof focal depths of the zoom lens, because of a foal depth relation,distance ranges to be covered are different at the time of the samepaying-out amount as shown. That is, only a width of Δ1/L_(T) can becovered for focusing at the tele (T) time, while a larger width ofΔ1/L_(T) can be covered at the wide (W) time.

Considering such a relation, step S263 in the flowchart of FIG. 54 mustbe switched.

In step S261, an average value of inverse numbers of distances of allpoints obtained in multidistance measuring is calculated as 1/L_(AV).Then, in step S262, an absolute value of a difference between theaverage 1/L_(AV) and an inverse number 1/L of a main object distance isobtained as Δ1/L. If a difference between both is large, it means thatthe main object is far from the background, and it can be understoodthat there is a scene similar to that shown in FIG. 45A.

On the other hand, if the difference is small, it can be understood thatthe main object and the other object are close to each other. That is,it can be understood that there is a scene similar to that shown in FIG.45B. However, if the lens is on the wide side, since an object depth islarge, focus can be set on both of the main object and the backgroundeven if they are not so close to each other.

Considering such a relation, branch determination is made in step S263.That is, determination is made as to whether the zoom position is tele(T) or not. If the zoom position is tele, the process moves to stepS264, and to step S265 if not.

In step S264, a result Δ1/L obtained in step S262 is compared with apredetermined value Δ1/L_(T). If a result shows that the Δ1/L is larger,the process moves to step S266, and to step S267 if not.

Similarly, in step S265, the result Δ1/L obtained in step S262 iscompared with a predetermined value Δ1/LW. If a result shows that theΔ1/L is larger, the process moves to step S266, and to step S267 if not.

In step S266, a large distance difference is determined, while a smalldistance difference is determined in step S267. By making branchdetermination of step S233 in the flowchart of FIG. 51 based on suchdetermination results, a situation of FIG. 45A or FIG. 45B can bedetermined, and the imager AF or the external light AF can be decided.

In place of the determination step S233 of obtaining the differencebetween the main object distance and the other distance in the flowchartof FIG. 51, determination similar to that shown in a flowchart of FIG.56 may be carried out based on the number of objects included in apredetermined distance range.

That is, in step S271, determination is first made as to whether a zoomposition is tele (T) or not. If the zoom position is tele, the processmoves to step S272, and if not, the process moves to step S273.

In step S272, with respect to the inverse number 1/L of the main objectdistance, the number of distance measuring points included in the rangeof the inverse number Δ1/L_(T) of a switched distance is set to n.Similarly, in step S273, with respect to the inverse number 1/L of themain object distance, the number of distance measuring points includedin a range of the inverse number Δ1/1_(W) of a switched distance is setto n.

Then, in step S274, among all the distance measuring points ofmultidistance measuring, determination is made as to whether n obtainedin step S272 or step S273 is larger than 50% or not. If it is largerthan 50%, the process moves to step S275 to determine that a distancedifference is small. On the other hand, if it is equal to/lower than50%, the process moves to step S276 to determine that a distancedifference is large.

Based on such result, scene determination may be carried out.

As described above, since a distance relation between the main objectand the other object can be easily obtained by the determination methodwhich uses simple calculation and comparison, it is possible to providean AF camera which determines a scene at a high speed to enable accurateswitching of an autofocus system which gives priority to a speed orfocusing, and never loses a photo opportunity.

Next, a thirteenth embodiment will be described.

According to the foregoing eleventh and twelfth embodiments, thephotographing scene is determined only based on the distancedistribution. However, the invention is not limited to suchdetermination. For example, as shown in FIG. 45C, if the main object 192a is located on the end of the screen 190, the background is alsoconsidered to be an important object and, even if the backgrounddistance is far, the operation may be switched to the AF which givespriority to the external light AF. In such an application case, in theflowchart of FIG. 51, a branch of determining an object position may beinserted between steps S233 and S235, and the process may be branched tostep S234 if the main object is located on the end.

In addition to the distance distribution and the object position, aphotographing scene may be determined based on a state of an imagesignal on the screen.

That is, in the scenes of FIGS. 45A and 45B, image data (main object)192 m obtained by the sensor arrays of the external light AF becomesimilar to those shown in FIGS. 57 and 58A. That is, in FIG. 45A, thebackground is only a monotonous shade and, in FIG. 45B, there arevarious shades because various objects are present. In the case of suchimage data, great fluctuation characteristically occurs. To determinesuch characteristics, the amount of adjacent data is calculated to formso-called differentiation data. Accordingly, large data is generated ina place of changes, and data of a graph shown in FIG. 58B is obtained.

As shown in FIG. 58B, by investigating whether the differentiation dataexceeds a predetermined value or not, it is possible to determinewhether the scene in the screen is simple or rough.

FIG. 59 is a flowchart explaining a distance measuring operation of thecamera which uses the image data obtained by external light distancemeasuring or the like, and determines a photographing scene to switchbetween the external light AF and the imager AF.

That is, first, in step S281, an image signal is detected by theexternal light AF sensor. Then, in step S282, a detection result of stepS281 is used to carry out multipoint distance measuring. Then, in stepS283, based on a result of step S282, data indicating a nearest distanceis set for a main object distance.

In step S284, a point of the distance L obtained in step S283 is set asa main object. In subsequent step S285, differential value calculationwhich is a feature of the thirteenth embodiment is carried out.

Then, in step S286, as described above, the number of points whichexceeds a predetermined amount is investigated, and this number iscompared with a predetermined value n₀. If a result shows that thenumber is smaller than the predetermined value no, the process moves tostep S288, and to step S287 if not.

In step S287, distance measuring by an external light is executed tofocus on the distance L. Then, the process moves to step S292 to executephotographing.

On the other hand, in step S288, the taking lens is driven before thelens position equivalent to the main object distance L. Then, in stepS289, contrast detection is started. Then, in step S290, a lens positionof maximum contrast is detected. If contrast is not maximum, the processmoves to step S291 to finely adjust the lens position, and a position ofjust focusing is searched.

Thus, until the position of maximum contrast is found, the process ofsteps S289 to S291 is repeated. After the position of maximum contrastis reached, focus is set on the position, and photographing is executedin step S292.

That is, focusing by the imager AF after step S288 or the external lightAF after step S287 is switched. That is, considering that a scene havingmore differential time peaks is a rough scene, there are variousobjects, and these are also regarded as important objects. Conversely,in a scene of a smaller number of peaks, the main object is consideredmost important, and AF which gives priority to focusing is carried out.

As described above, according to the thirteenth embodiment, since scenedetermination is carried out by using the state of image distribution inthe screen, it is possible to select an AF system most suited to thesituation.

Incidentally, a contrast change of the object state can be determined byusing not only the external distance measuring sensor arrays and theimager outputs but also the distance measuring sensor for cameraexposure matching.

In most of the digital cameras, exposure control is carried out by usingthe CCD, but a camera similar to that shown in FIG. 60, on which aphotometry sensor capable of instantaneous photometry of even lowluminance, is available.

FIG. 60 is a schematic sectional view showing a constitution of a cameraaccording to a fourteenth embodiment of the present invention.

In FIG. 60, a taking lens 252 is attached to the front of a camera mainbody 250. A half mirror 254 is disposed on an optical axis after thetaking lens 252.

A CCD 266 which is an imager is arranged after the half mirror 254. Ascreen 256 and a pentaprism 258 are arranged above the half mirror 254.Thus, an object image made incident from the taking lens 258 isreflected on the half mirror 254 to be projected to the screen 256, andpassed through the pentaprism 258 to be observed by an eye 160 of aphotographer.

An external light optical system 262 is disposed between the screen 256and the pentaprism 258. A photometry sensor 264 is arranged in aposition which enables monitoring of an object image through thepentaprism 258. This photometry sensor 264 is divided, and can carry outphotometry of a plurality of points, e.g., in a screen 278 like thatshown in FIG. 61.

By using the photometry sensor of such a constitution, it is possible tomeasure a luminance distribution of the entire screen even if resolutionis not as high as the CCD.

The embodiment can be applied to contrast determination which uses sucha photometry sensor, and switching of an AF system.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventionconcept as defined by the appended claims and their equivalents.

1. A camera comprising: a taking lens; a first focus adjustment sectionwhich adjusts a focusing position of the taking lens; a second focusadjustment section which has accuracy lower than that of the first focusadjustment section but which adjusts the focusing position of the takinglens at a high speed; an imaging section which includes an imager toimage an object image through the taking lens, and converts an outputsignal of the imager into image data; a compressibility setting sectionwhich sets a compressibility of the image data obtained in the imagingsection; a compression section which compresses the image data inaccordance with the compressibility set in the compressibility settingsection; and a deciding section which decides one of the first focusadjustment section and the second focus adjustment section which isemployed to carry out a final focus adjustment operation of the takinglens in accordance with the compressibility set in the compressibilitysetting section.
 2. The camera according to claim 1, wherein the firstfocus adjustment section adjusts the focusing position of the takinglens by detecting a contrast change of the image data outputted from theimaging section during movement of the taking lens, and the second focusadjustment section includes a section to output a signal dependent on adistance of an object, and adjusts the focusing position of the takinglens in accordance with an output result of the section.
 3. The cameraaccording to claim 1, wherein the deciding section selects the firstfocus adjustment section when a first compressibility is set by thecompressibility setting section, and the second focus adjustment sectionwhen a second compressibility smaller in compression rate than the firstcompressibility is set.
 4. The camera according to claim 1, wherein thefirst focus adjustment section carries out a focus adjustment by animager AF system, and the second focus adjustment section carries out afocus adjustment operation by an external light AF system or a TTL phasedifference AF system.
 5. A camera comprising: a taking lens; an imagingsection which includes an imager to image an object image through thetaking lens, and converts an output signal of the imager into imagedata; a first focus adjustment section which adjusts a focusing positionof the taking lens by detecting a contrast change of the image dataoutputted from the imaging section during movement of the taking lens; asecond focus adjustment section which includes a section to output asignal dependent on a distance of an object, and adjusts the focusingposition of the taking lens in accordance with an output result of thesection; an image processing section which carries out predeterminedprocessing for the image data outputted from the imaging section; and acontrol section which causes one of the first focus adjustment sectionand the second focus adjustment section to execute a final focusadjustment operation for the taking lens in accordance with a processingcontent of the image processing section.
 6. The camera according toclaim 5, wherein the image processing section includes a section tocompress the image data obtained in the imaging section by apredetermined compressibility, and the control section causes one of thefocus adjustment sections to execute a final operation based on thecompressibility.
 7. The camera according to claim 5, wherein the imageprocessing section includes a section to convert the image data obtainedin the imaging section into a predetermined image size, and the controlsection causes one of the focus adjustment sections to execute a finaloperation based on the predetermined image size.
 8. The camera accordingto claim 5, wherein the image processing section includes a section tocarry out edge emphasis processing for the image data obtained in theimaging section, and the control section causes one of the focusadjustment sections to execute a final operation based on presence ofthe edge emphasis processing.
 9. A camera comprising: a taking lens; animaging section which includes an imager to image an object imagethrough the taking lens, and converts an output signal of the imagerinto image data; a compressibility setting section which sets acompressibility of the image data obtained in the imaging section; acompression section which compresses the image data in accordance withthe compressibility set in the compressibility setting section; a firstfocus adjustment section which adjusts a focusing position of the takinglens by detecting a contrast change of the image data outputted from theimaging section during movement of the taking lens; a second focusadjustment section which includes a section to output a signal dependenton a distance of an object, and adjusts the focusing position of thetaking lens in accordance with an output result of the section; and acontrol section which operates the second focus adjustment section alonewhen the compressibility set in the compressibility setting section is afirst compressibility, and which operates the first focus adjustmentsection after the second focus adjustment section when thecompressibility is a second compressibility lower than the firstcompressibility.
 10. A camera comprising: a taking lens; an imager whichimages an object image through the taking lens; an image processingcircuit which generates digital image data from an output of the imager,and includes a compression circuit to compress the image data at acompressibility selected from a plurality of compressibilities; a focusadjustment mechanism which adjusts a focusing position of the takinglens; a distance measuring circuit which detects a distance of an objector a focus deviation amount of the taking lens; and a CPU which receivesthe output of the imager and an output of the distance measuringcircuit, controls the focus adjustment mechanism based on the receivedoutputs, and decides a control form of the focus adjustment mechanism inaccordance with the compressibility selected by the compression circuit.11. The camera according to claim 10, wherein the CPU controls the focusadjustment mechanism based on only the output of the distance measuringcircuit when the selected compressibility is a first compressibility,and uses a focus adjustment based on the output of the imager incombination with a focus adjustment based on the output of the distancemeasuring circuit when the selected compressibility is a secondcompressibility lower than the first compressibility.
 12. The cameraaccording to claim 10, wherein the CPU has a first control form tocontrol the focus adjustment mechanism based on a contrast value of theimage data outputted from the image processing circuit, and a secondcontrol form to control the focus adjustment mechanism based on theoutput of the distance measuring circuit.